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Allowance for Loan Losses (Details) (USD $) | 3 Months Ended | 12 Months Ended
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Dec. 31, 2014 | Sep. 30, 2014 | Jun. 30, 2014 | Mar. 31, 2014 | Dec. 31, 2013 | Sep. 30, 2013 | Jun. 30, 2013 | Mar. 31, 2013 | Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Allowance for Loans Evaluated Individually for Impairment | $ 1,803,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 |  |  |  | $ 2,461,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 |  |  |  | $ 1,803,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 | $ 2,461,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 | $ 3,539,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
Allowance for Loans Evaluated Collectively for Impairment | 8,541,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment |  |  |  | 9,053,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment |  |  |  | 8,541,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment | 9,053,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment | 8,961,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
Total Allowance for Loan Losses | 10,344,000 us-gaap_LoansAndLeasesReceivableAllowance |  |  |  | 11,514,000 us-gaap_LoansAndLeasesReceivableAllowance |  |  |  | 10,344,000 us-gaap_LoansAndLeasesReceivableAllowance | 11,514,000 us-gaap_LoansAndLeasesReceivableAllowance | 12,500,000 us-gaap_LoansAndLeasesReceivableAllowance
Total Allowance for Loan Losses | 10,344,000 us-gaap_LoansAndLeasesReceivableAllowance |  |  |  | 11,514,000 us-gaap_LoansAndLeasesReceivableAllowance |  |  |  | 10,344,000 us-gaap_LoansAndLeasesReceivableAllowance | 11,514,000 us-gaap_LoansAndLeasesReceivableAllowance | 12,500,000 us-gaap_LoansAndLeasesReceivableAllowance
Commercial and municipal risk-rated loans receivable | 398,198,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable |  |  |  | 380,731,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable |  |  |  | 398,198,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable | 380,731,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Beginning balance |  |  |  | 11,514,000 us-gaap_LoansAndLeasesReceivableAllowance |  |  |  | 12,500,000 us-gaap_LoansAndLeasesReceivableAllowance | 11,514,000 us-gaap_LoansAndLeasesReceivableAllowance | 12,500,000 us-gaap_LoansAndLeasesReceivableAllowance | 13,000,000 us-gaap_LoansAndLeasesReceivableAllowance
Chargeoffs |  |  |  |  |  |  |  |  | 3,495,000 us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs | 5,855,000 us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs | 9,080,000 us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs
Recoveries |  |  |  |  |  |  |  |  | 1,175,000 us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts | 669,000 us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts | 745,000 us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts
Provision for loan losses | 300,000 us-gaap_ProvisionForLoanAndLeaseLosses | 350,000 us-gaap_ProvisionForLoanAndLeaseLosses | 100,000 us-gaap_ProvisionForLoanAndLeaseLosses | 400,000 us-gaap_ProvisionForLoanAndLeaseLosses | 700,000 us-gaap_ProvisionForLoanAndLeaseLosses | 800,000 us-gaap_ProvisionForLoanAndLeaseLosses | 1,200,000 us-gaap_ProvisionForLoanAndLeaseLosses | 1,500,000 us-gaap_ProvisionForLoanAndLeaseLosses | 1,150,000 us-gaap_ProvisionForLoanAndLeaseLosses | 4,200,000 us-gaap_ProvisionForLoanAndLeaseLosses | 7,835,000 us-gaap_ProvisionForLoanAndLeaseLosses
Ending balance | 10,344,000 us-gaap_LoansAndLeasesReceivableAllowance |  |  |  | 11,514,000 us-gaap_LoansAndLeasesReceivableAllowance |  |  |  | 10,344,000 us-gaap_LoansAndLeasesReceivableAllowance | 11,514,000 us-gaap_LoansAndLeasesReceivableAllowance | 12,500,000 us-gaap_LoansAndLeasesReceivableAllowance
Ending balance specifically evaluated for impairment | 1,803,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 |  |  |  | 2,461,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 |  |  |  | 1,803,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 | 2,461,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 | 3,539,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
Ending balance collectively evaluated for impairment | 8,541,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment |  |  |  | 9,053,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment |  |  |  | 8,541,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment | 9,053,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment | 8,961,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
Related loan balances |  |  |  |  |  |  |  |  |  |  |
Ending balance | 917,564,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome |  |  |  | 876,367,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome |  |  |  | 917,564,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome | 876,367,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome | 869,284,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
Ending balance specifically evaluated for impairment | 35,862,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment |  |  |  | 42,351,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment |  |  |  | 35,862,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment | 42,351,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment | 45,744,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment
Ending balance collectively evaluated for impairment | 881,702,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment |  |  |  | 834,016,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment |  |  |  | 881,702,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment | 834,016,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment | 823,540,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Allowance for Loan and Lease Losses, Related Loans, Percentage |  |  |  |  |  |  |  |  | 0.39%fnlc_AllowanceforLoanandLeaseLossesRelatedLoansPercentage | 0.40%fnlc_AllowanceforLoanandLeaseLossesRelatedLoansPercentage |
Allowance for Loan and Lease Losses, Related Loans, Period Increase (Decrease) |  |  |  |  |  |  |  |  | 128,000 fnlc_AllowanceforLoanandLeaseLossesRelatedLoansPeriodIncreaseDecrease |  |
Total Allowance for Loan Losses | 10,344,000 us-gaap_LoansAndLeasesReceivableAllowance |  |  |  | 11,514,000 us-gaap_LoansAndLeasesReceivableAllowance |  |  |  | 10,344,000 us-gaap_LoansAndLeasesReceivableAllowance | 11,514,000 us-gaap_LoansAndLeasesReceivableAllowance | 12,500,000 us-gaap_LoansAndLeasesReceivableAllowance
Allowance for loan and lease losses unallocated portion, period increase (decrease) |  |  |  |  |  |  |  |  | 16,000 fnlc_Fnlc_AllowanceforLoanandLeaseLossesUnallocatedPortionPeriodIncreasedecrease |  |
Average loan growth |  |  |  |  |  |  |  |  | 0.030 fnlc_AverageLoanGrowth |  |
Other Real Estate, Average Percentage of Sales Price below Appraised Value |  |  |  |  |  |  |  |  | 20.00%fnlc_OtherRealEstateAveragePercentageofSalesPricebelowAppraisedValue |  |
Other Real Estate, Additional Discount Percentage to Calculate Allowances for Losses |  |  |  |  |  |  |  |  | 20.00%fnlc_OtherRealEstateAdditionalDiscountPercentagetoCalculateAllowancesforLosses |  |
Risk Based Ratios, Weighted-Average Required Reserve as Percent of Total Loans |  |  |  |  |  |  |  |  |  | 1.33%fnlc_RiskBasedRatiosWeightedAverageRequiredReserveasPercentofTotalLoans |
Allowance for Loan Losses of Total Loans, Percentage | 1.13%fnlc_AllowanceforLoanLossesofTotalLoansPercentage |  |  |  | 1.31%fnlc_AllowanceforLoanLossesofTotalLoansPercentage |  |  |  | 1.13%fnlc_AllowanceforLoanLossesofTotalLoansPercentage | 1.31%fnlc_AllowanceforLoanLossesofTotalLoansPercentage |
Commercial real estate loans maximum loan-to-value (in hundredths) | 75.00%fnlc_CommercialRealEstateLoansMaximumLoanToValue |  |  |  |  |  |  |  | 75.00%fnlc_CommercialRealEstateLoansMaximumLoanToValue |  |
Construction loans actual loan portfolio-to-Company capital (in hundredths) | 31.30%fnlc_ConstructionLoansActualLoanPortfolioToCompanyCapital |  |  |  |  |  |  |  | 31.30%fnlc_ConstructionLoansActualLoanPortfolioToCompanyCapital |  |
Construction loans maximum loan portfolio-to-Company capital (in hundredths) | 100.00%fnlc_ConstructionLoanPortfolioMaximumToCompanyCapital |  |  |  |  |  |  |  | 100.00%fnlc_ConstructionLoanPortfolioMaximumToCompanyCapital |  |
Construction and non-owner-occupied commercial real estate loan portfolio-to-Company Capital (in hundredths) | 94.70%fnlc_ConstructionAndNonOwnerOccupiedCommercialRealEstateLoansPortfolioToCompanyCapital |  |  |  |  |  |  |  | 94.70%fnlc_ConstructionAndNonOwnerOccupiedCommercialRealEstateLoansPortfolioToCompanyCapital |  |
Construction and non-owner-occupied commercial real estate loan portfolio loan-to-Company capital (in hundredths) | 300.00%fnlc_ConstructionAndNonOwnerOccupiedCommercialRealEstateLoansMaximumLoanPortfolioToCompanyCapital |  |  |  |  |  |  |  | 300.00%fnlc_ConstructionAndNonOwnerOccupiedCommercialRealEstateLoansMaximumLoanPortfolioToCompanyCapital |  |
Residential loans typical loan-to-value range, low (in hundredths) | 75.00%fnlc_ResidentialLoansTypicalLoanToValueRangeLow |  |  |  |  |  |  |  | 75.00%fnlc_ResidentialLoansTypicalLoanToValueRangeLow |  |
Residential loans typical loan-to-value maximum (in hundredths) | 80.00%fnlc_ResidentialLoansTypicalLoanToValueRangeHigh |  |  |  |  |  |  |  | 80.00%fnlc_ResidentialLoansTypicalLoanToValueRangeHigh |  |
Collateralized consumer loans to individuals loan-to-value maximum range, low (in hundredths) | 80.00%fnlc_CollateralizedConsumerLoansToIndividualsLoanToValueMaximumRangeLow |  |  |  |  |  |  |  | 80.00%fnlc_CollateralizedConsumerLoansToIndividualsLoanToValueMaximumRangeLow |  |
Collateralized consumer loans to individuals loan-to-value maximum range, high (in hundredths) | 90.00%fnlc_CollateralizedConsumerLoansToIndividualsLoanToValueMaximumRangeHigh |  |  |  |  |  |  |  | 90.00%fnlc_CollateralizedConsumerLoansToIndividualsLoanToValueMaximumRangeHigh |  |
Delinquent period before residential loans placed on non-accrual status (in days) |  |  |  |  |  |  |  |  | 90 days |  |
Delinquent period before consumer loans charged off (in days) |  |  |  |  |  |  |  |  | 120 days |  |
Strong 1 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 342,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_InternalCreditAssessmentAxis = fnlc_Strong1Member |  |  |  | 281,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_InternalCreditAssessmentAxis = fnlc_Strong1Member |  |  |  | 342,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_InternalCreditAssessmentAxis = fnlc_Strong1Member | 281,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_InternalCreditAssessmentAxis = fnlc_Strong1Member |
Above Average 2 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 39,438,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_InternalCreditAssessmentAxis = fnlc_AboveAverage2Member |  |  |  | 38,318,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_InternalCreditAssessmentAxis = fnlc_AboveAverage2Member |  |  |  | 39,438,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_InternalCreditAssessmentAxis = fnlc_AboveAverage2Member | 38,318,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_InternalCreditAssessmentAxis = fnlc_AboveAverage2Member |
Satisfactory 3 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 78,125,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_InternalCreditAssessmentAxis = fnlc_Satisfactory3Member |  |  |  | 63,823,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_InternalCreditAssessmentAxis = fnlc_Satisfactory3Member |  |  |  | 78,125,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_InternalCreditAssessmentAxis = fnlc_Satisfactory3Member | 63,823,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_InternalCreditAssessmentAxis = fnlc_Satisfactory3Member |
Average 4 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 176,959,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_InternalCreditAssessmentAxis = fnlc_Average4Member |  |  |  | 161,073,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_InternalCreditAssessmentAxis = fnlc_Average4Member |  |  |  | 176,959,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_InternalCreditAssessmentAxis = fnlc_Average4Member | 161,073,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_InternalCreditAssessmentAxis = fnlc_Average4Member |
Watch 5 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 56,712,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_InternalCreditAssessmentAxis = fnlc_Watch5Member |  |  |  | 42,791,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_InternalCreditAssessmentAxis = fnlc_Watch5Member |  |  |  | 56,712,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_InternalCreditAssessmentAxis = fnlc_Watch5Member | 42,791,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_InternalCreditAssessmentAxis = fnlc_Watch5Member |
OAEM 6 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 14,335,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_InternalCreditAssessmentAxis = fnlc_Oaem6Member |  |  |  | 32,288,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_InternalCreditAssessmentAxis = fnlc_Oaem6Member |  |  |  | 14,335,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_InternalCreditAssessmentAxis = fnlc_Oaem6Member | 32,288,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_InternalCreditAssessmentAxis = fnlc_Oaem6Member |
Substandard 7 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 32,287,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember |  |  |  | 41,532,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember |  |  |  | 32,287,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember | 41,532,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember |
Doubtful 8 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember |  |  |  | 625,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember |  |  |  | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember | 625,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember |
Specific Reserves Evaluated Individually for Impairment |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 1,803,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember |  |  |  | 2,461,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember |  |  |  | 1,803,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember | 2,461,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember |
Total Allowance for Loan Losses | 1,803,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember |  |  |  | 2,461,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember |  |  |  | 1,803,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember | 2,461,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 1,803,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember |  |  |  | 2,461,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember |  |  |  | 1,803,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember | 2,461,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 1,803,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember |  |  |  | 2,461,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember |  |  |  | 1,803,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember | 2,461,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember |
General Reserves Based on Historical Loss Experience |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 3,282,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember |  |  |  | 3,906,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember |  |  |  | 3,282,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember | 3,906,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember |
Total Allowance for Loan Losses | 3,282,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember |  |  |  | 3,906,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember |  |  |  | 3,282,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember | 3,906,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 3,282,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember |  |  |  | 3,906,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember |  |  |  | 3,282,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember | 3,906,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 3,282,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember |  |  |  | 3,906,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember |  |  |  | 3,282,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember | 3,906,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember |
Reserve for Qualitative Factors |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 3,597,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember |  |  |  | 3,469,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember |  |  |  | 3,597,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember | 3,469,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember |
Total Allowance for Loan Losses | 3,597,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember |  |  |  | 3,469,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember |  |  |  | 3,597,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember | 3,469,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 3,597,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember |  |  |  | 3,469,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember |  |  |  | 3,597,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember | 3,469,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 3,597,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember |  |  |  | 3,469,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember |  |  |  | 3,597,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember | 3,469,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember |
Unallocated Reserves |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 1,662,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember |  |  |  | 1,678,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember |  |  |  | 1,662,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember | 1,678,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember |
Total Allowance for Loan Losses | 1,662,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember |  |  |  | 1,678,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember |  |  |  | 1,662,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember | 1,678,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 1,662,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember |  |  |  | 1,678,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember |  |  |  | 1,662,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember | 1,678,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 1,662,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember |  |  |  | 1,678,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember |  |  |  | 1,662,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember | 1,678,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember |
Percentage of Total Reserve Allowance accounted for by Loan Loss Allowances | 16.10%fnlc_PercentageofTotalReserveAllowanceaccountedforbyLoanLossAllowances / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember |  |  |  | 14.60%fnlc_PercentageofTotalReserveAllowanceaccountedforbyLoanLossAllowances / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember |  |  |  | 16.10%fnlc_PercentageofTotalReserveAllowanceaccountedforbyLoanLossAllowances / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember | 14.60%fnlc_PercentageofTotalReserveAllowanceaccountedforbyLoanLossAllowances / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember |
Commercial Real Estate |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Allowance for Loans Evaluated Individually for Impairment | 346,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 890,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 346,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 890,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 1,523,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember
Allowance for Loans Evaluated Collectively for Impairment | 3,186,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 3,712,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 3,186,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 3,712,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 4,342,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember
Total Allowance for Loan Losses | 3,532,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 4,602,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 3,532,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 4,602,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 5,865,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember
Total Allowance for Loan Losses | 3,532,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 4,602,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 3,532,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 4,602,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 5,865,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember
Commercial and municipal risk-rated loans receivable | 242,311,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 245,943,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 242,311,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 245,943,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Beginning balance |  |  |  | 4,602,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 5,865,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 4,602,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 5,865,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 5,659,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember
Chargeoffs |  |  |  |  |  |  |  |  | 1,205,000 us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 150,000 us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 1,394,000 us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember
Recoveries |  |  |  |  |  |  |  |  | 144,000 us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 0 us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 13,000 us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember
Provision for loan losses |  |  |  |  |  |  |  |  | (9,000)us-gaap_ProvisionForLoanAndLeaseLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | (1,113,000)us-gaap_ProvisionForLoanAndLeaseLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 1,587,000 us-gaap_ProvisionForLoanAndLeaseLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember
Ending balance | 3,532,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 4,602,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 3,532,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 4,602,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 5,865,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember
Ending balance specifically evaluated for impairment | 346,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 890,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 346,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 890,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 1,523,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember
Ending balance collectively evaluated for impairment | 3,186,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 3,712,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 3,186,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 3,712,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 4,342,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember
Related loan balances |  |  |  |  |  |  |  |  |  |  |
Ending balance | 242,311,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 245,943,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 242,311,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 245,943,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 251,335,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember
Ending balance specifically evaluated for impairment | 13,304,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 14,935,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 13,304,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 14,935,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 15,774,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember
Ending balance collectively evaluated for impairment | 229,007,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 231,008,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 229,007,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 231,008,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 235,561,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 3,532,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 4,602,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 3,532,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 4,602,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 5,865,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember
Commercial Real Estate | Strong 1 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 12,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Strong1Member |  |  |  | 16,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Strong1Member |  |  |  | 12,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Strong1Member | 16,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Strong1Member |
Commercial Real Estate | Above Average 2 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 12,668,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = fnlc_AboveAverage2Member |  |  |  | 14,565,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = fnlc_AboveAverage2Member |  |  |  | 12,668,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = fnlc_AboveAverage2Member | 14,565,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = fnlc_AboveAverage2Member |
Commercial Real Estate | Satisfactory 3 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 50,275,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Satisfactory3Member |  |  |  | 45,213,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Satisfactory3Member |  |  |  | 50,275,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Satisfactory3Member | 45,213,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Satisfactory3Member |
Commercial Real Estate | Average 4 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 108,719,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Average4Member |  |  |  | 100,343,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Average4Member |  |  |  | 108,719,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Average4Member | 100,343,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Average4Member |
Commercial Real Estate | Watch 5 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 36,974,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Watch5Member |  |  |  | 32,326,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Watch5Member |  |  |  | 36,974,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Watch5Member | 32,326,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Watch5Member |
Commercial Real Estate | OAEM 6 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 9,846,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Oaem6Member |  |  |  | 26,102,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Oaem6Member |  |  |  | 9,846,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Oaem6Member | 26,102,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Oaem6Member |
Commercial Real Estate | Substandard 7 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 23,817,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember |  |  |  | 27,115,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember |  |  |  | 23,817,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember | 27,115,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember |
Commercial Real Estate | Doubtful 8 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember |  |  |  | 263,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember |  |  |  | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember | 263,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember |
Commercial Real Estate | Specific Reserves Evaluated Individually for Impairment |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 346,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 890,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 346,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 890,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |
Total Allowance for Loan Losses | 346,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 890,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 346,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 890,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 346,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 890,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 346,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 890,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 346,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 890,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 346,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 890,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |
Commercial Real Estate | General Reserves Based on Historical Loss Experience |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 1,444,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 1,927,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 1,444,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 1,927,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |
Total Allowance for Loan Losses | 1,444,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 1,927,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 1,444,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 1,927,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 1,444,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 1,927,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 1,444,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 1,927,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 1,444,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 1,927,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 1,444,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 1,927,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |
Commercial Real Estate | Reserve for Qualitative Factors |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 1,742,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 1,785,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 1,742,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 1,785,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |
Total Allowance for Loan Losses | 1,742,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 1,785,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 1,742,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 1,785,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 1,742,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 1,785,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 1,742,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 1,785,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 1,742,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 1,785,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 1,742,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 1,785,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |
Commercial Real Estate | Unallocated Reserves |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstatePortfolioSegmentMember |
Commercial Construction |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Allowance for Loans Evaluated Individually for Impairment | 413,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 272,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 413,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 272,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 969,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember
Allowance for Loans Evaluated Collectively for Impairment | 410,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 303,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 410,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 303,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 390,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember
Total Allowance for Loan Losses | 823,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 575,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 823,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 575,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 1,359,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember
Total Allowance for Loan Losses | 823,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 575,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 823,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 575,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 1,359,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember
Commercial and municipal risk-rated loans receivable | 30,932,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 20,382,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 30,932,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 20,382,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Beginning balance |  |  |  | 575,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 1,359,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 575,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 1,359,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 658,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember
Chargeoffs |  |  |  |  |  |  |  |  | 0 us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 963,000 us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 928,000 us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember
Recoveries |  |  |  |  |  |  |  |  | 0 us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 0 us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 246,000 us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember
Provision for loan losses |  |  |  |  |  |  |  |  | 248,000 us-gaap_ProvisionForLoanAndLeaseLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 179,000 us-gaap_ProvisionForLoanAndLeaseLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 1,383,000 us-gaap_ProvisionForLoanAndLeaseLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember
Ending balance | 823,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 575,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 823,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 575,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 1,359,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember
Ending balance specifically evaluated for impairment | 413,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 272,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 413,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 272,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 969,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember
Ending balance collectively evaluated for impairment | 410,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 303,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 410,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 303,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 390,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember
Related loan balances |  |  |  |  |  |  |  |  |  |  |
Ending balance | 30,932,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 20,382,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 30,932,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 20,382,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 22,417,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember
Ending balance specifically evaluated for impairment | 1,380,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 1,284,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 1,380,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 1,284,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 3,354,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember
Ending balance collectively evaluated for impairment | 29,552,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 19,098,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 29,552,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 19,098,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 19,063,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 823,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 575,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 823,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 575,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 1,359,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember
Commercial Construction | Strong 1 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Strong1Member |  |  |  | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Strong1Member |  |  |  | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Strong1Member | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Strong1Member |
Commercial Construction | Above Average 2 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 771,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = fnlc_AboveAverage2Member |  |  |  | 804,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = fnlc_AboveAverage2Member |  |  |  | 771,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = fnlc_AboveAverage2Member | 804,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = fnlc_AboveAverage2Member |
Commercial Construction | Satisfactory 3 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 1,983,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Satisfactory3Member |  |  |  | 871,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Satisfactory3Member |  |  |  | 1,983,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Satisfactory3Member | 871,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Satisfactory3Member |
Commercial Construction | Average 4 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 23,345,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Average4Member |  |  |  | 14,938,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Average4Member |  |  |  | 23,345,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Average4Member | 14,938,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Average4Member |
Commercial Construction | Watch 5 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 1,567,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Watch5Member |  |  |  | 26,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Watch5Member |  |  |  | 1,567,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Watch5Member | 26,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Watch5Member |
Commercial Construction | OAEM 6 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 2,519,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Oaem6Member |  |  |  | 2,948,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Oaem6Member |  |  |  | 2,519,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Oaem6Member | 2,948,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Oaem6Member |
Commercial Construction | Substandard 7 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 747,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember |  |  |  | 795,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember |  |  |  | 747,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember | 795,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember |
Commercial Construction | Doubtful 8 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember |  |  |  | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember |  |  |  | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember |
Commercial Construction | Specific Reserves Evaluated Individually for Impairment |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 413,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 272,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 413,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 272,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |
Total Allowance for Loan Losses | 413,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 272,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 413,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 272,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 413,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 272,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 413,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 272,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 413,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 272,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 413,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 272,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |
Commercial Construction | General Reserves Based on Historical Loss Experience |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 186,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 157,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 186,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 157,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |
Total Allowance for Loan Losses | 186,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 157,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 186,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 157,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 186,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 157,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 186,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 157,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 186,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 157,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 186,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 157,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |
Commercial Construction | Reserve for Qualitative Factors |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 224,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 146,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 224,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 146,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |
Total Allowance for Loan Losses | 224,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 146,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 224,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 146,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 224,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 146,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 224,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 146,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 224,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 146,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 224,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 146,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |
Commercial Construction | Unallocated Reserves |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialConstructionMember |
Commercial Other |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Allowance for Loans Evaluated Individually for Impairment | 129,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 841,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 129,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 841,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 652,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember
Allowance for Loans Evaluated Collectively for Impairment | 1,376,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 1,435,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 1,376,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 1,435,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 1,398,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember
Total Allowance for Loan Losses | 1,505,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 2,276,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 1,505,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 2,276,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 2,050,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember
Total Allowance for Loan Losses | 1,505,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 2,276,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 1,505,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 2,276,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 2,050,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember
Commercial and municipal risk-rated loans receivable | 104,531,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 95,289,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 104,531,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 95,289,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Beginning balance |  |  |  | 2,276,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 2,050,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 2,276,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 2,050,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 2,063,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember
Chargeoffs |  |  |  |  |  |  |  |  | 989,000 us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 2,583,000 us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 3,215,000 us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember
Recoveries |  |  |  |  |  |  |  |  | 758,000 us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 359,000 us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 113,000 us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember
Provision for loan losses |  |  |  |  |  |  |  |  | (540,000)us-gaap_ProvisionForLoanAndLeaseLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 2,450,000 us-gaap_ProvisionForLoanAndLeaseLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 3,089,000 us-gaap_ProvisionForLoanAndLeaseLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember
Ending balance | 1,505,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 2,276,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 1,505,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 2,276,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 2,050,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember
Ending balance specifically evaluated for impairment | 129,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 841,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 129,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 841,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 652,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember
Ending balance collectively evaluated for impairment | 1,376,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 1,435,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 1,376,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 1,435,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 1,398,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember
Related loan balances |  |  |  |  |  |  |  |  |  |  |
Ending balance | 104,531,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 95,289,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 104,531,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 95,289,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 81,183,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember
Ending balance specifically evaluated for impairment | 2,942,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 6,698,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 2,942,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 6,698,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 5,861,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember
Ending balance collectively evaluated for impairment | 101,589,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 88,591,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 101,589,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 88,591,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 75,322,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 1,505,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 2,276,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 1,505,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 2,276,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 2,050,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember
Commercial Other | Strong 1 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 330,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Strong1Member |  |  |  | 265,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Strong1Member |  |  |  | 330,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Strong1Member | 265,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Strong1Member |
Commercial Other | Above Average 2 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 7,210,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember / us-gaap_InternalCreditAssessmentAxis = fnlc_AboveAverage2Member |  |  |  | 6,719,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember / us-gaap_InternalCreditAssessmentAxis = fnlc_AboveAverage2Member |  |  |  | 7,210,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember / us-gaap_InternalCreditAssessmentAxis = fnlc_AboveAverage2Member | 6,719,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember / us-gaap_InternalCreditAssessmentAxis = fnlc_AboveAverage2Member |
Commercial Other | Satisfactory 3 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 24,232,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Satisfactory3Member |  |  |  | 14,852,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Satisfactory3Member |  |  |  | 24,232,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Satisfactory3Member | 14,852,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Satisfactory3Member |
Commercial Other | Average 4 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 44,895,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Average4Member |  |  |  | 45,792,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Average4Member |  |  |  | 44,895,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Average4Member | 45,792,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Average4Member |
Commercial Other | Watch 5 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 18,171,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Watch5Member |  |  |  | 10,439,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Watch5Member |  |  |  | 18,171,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Watch5Member | 10,439,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Watch5Member |
Commercial Other | OAEM 6 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 1,970,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Oaem6Member |  |  |  | 3,238,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Oaem6Member |  |  |  | 1,970,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Oaem6Member | 3,238,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Oaem6Member |
Commercial Other | Substandard 7 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 7,723,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember |  |  |  | 13,622,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember |  |  |  | 7,723,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember | 13,622,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember |
Commercial Other | Doubtful 8 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember |  |  |  | 362,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember |  |  |  | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember | 362,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember |
Commercial Other | Specific Reserves Evaluated Individually for Impairment |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 129,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 841,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 129,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 841,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |
Total Allowance for Loan Losses | 129,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 841,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 129,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 841,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 129,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 841,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 129,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 841,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 129,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 841,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 129,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 841,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |
Commercial Other | General Reserves Based on Historical Loss Experience |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 624,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 745,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 624,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 745,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |
Total Allowance for Loan Losses | 624,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 745,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 624,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 745,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 624,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 745,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 624,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 745,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 624,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 745,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 624,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 745,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |
Commercial Other | Reserve for Qualitative Factors |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 752,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 690,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 752,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 690,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |
Total Allowance for Loan Losses | 752,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 690,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 752,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 690,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 752,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 690,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 752,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 690,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 752,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 690,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 752,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 690,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |
Commercial Other | Unallocated Reserves |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_CommercialOtherMember |
Municipal |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Allowance for Loans Evaluated Individually for Impairment | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember
Allowance for Loans Evaluated Collectively for Impairment | 15,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 15,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 15,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 15,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 18,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember
Total Allowance for Loan Losses | 15,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 15,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 15,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 15,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 18,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember
Total Allowance for Loan Losses | 15,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 15,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 15,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 15,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 18,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember
Commercial and municipal risk-rated loans receivable | 20,424,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 19,117,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 20,424,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 19,117,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Beginning balance |  |  |  | 15,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 18,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 15,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 18,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 19,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember
Chargeoffs |  |  |  |  |  |  |  |  | 0 us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 0 us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 0 us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember
Recoveries |  |  |  |  |  |  |  |  | 0 us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 0 us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 0 us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember
Provision for loan losses |  |  |  |  |  |  |  |  | 0 us-gaap_ProvisionForLoanAndLeaseLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | (3,000)us-gaap_ProvisionForLoanAndLeaseLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | (1,000)us-gaap_ProvisionForLoanAndLeaseLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember
Ending balance | 15,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 15,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 15,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 15,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 18,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember
Ending balance specifically evaluated for impairment | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember
Ending balance collectively evaluated for impairment | 15,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 15,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 15,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 15,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 18,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember
Related loan balances |  |  |  |  |  |  |  |  |  |  |
Ending balance | 20,424,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 19,117,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 20,424,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 19,117,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 14,704,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember
Ending balance specifically evaluated for impairment | 0 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 0 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 0 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 0 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 0 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember
Ending balance collectively evaluated for impairment | 20,424,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 19,117,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 20,424,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 19,117,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 14,704,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 15,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 15,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 15,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 15,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 18,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember
Municipal | Strong 1 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Strong1Member |  |  |  | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Strong1Member |  |  |  | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Strong1Member | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Strong1Member |
Municipal | Above Average 2 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 18,789,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember / us-gaap_InternalCreditAssessmentAxis = fnlc_AboveAverage2Member |  |  |  | 16,230,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember / us-gaap_InternalCreditAssessmentAxis = fnlc_AboveAverage2Member |  |  |  | 18,789,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember / us-gaap_InternalCreditAssessmentAxis = fnlc_AboveAverage2Member | 16,230,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember / us-gaap_InternalCreditAssessmentAxis = fnlc_AboveAverage2Member |
Municipal | Satisfactory 3 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 1,635,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Satisfactory3Member |  |  |  | 2,887,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Satisfactory3Member |  |  |  | 1,635,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Satisfactory3Member | 2,887,000 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Satisfactory3Member |
Municipal | Average 4 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Average4Member |  |  |  | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Average4Member |  |  |  | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Average4Member | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Average4Member |
Municipal | Watch 5 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Watch5Member |  |  |  | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Watch5Member |  |  |  | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Watch5Member | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Watch5Member |
Municipal | OAEM 6 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Oaem6Member |  |  |  | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Oaem6Member |  |  |  | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Oaem6Member | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember / us-gaap_InternalCreditAssessmentAxis = fnlc_Oaem6Member |
Municipal | Substandard 7 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember |  |  |  | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember |  |  |  | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember |
Municipal | Doubtful 8 |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commercial and municipal risk-rated loans receivable | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember |  |  |  | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember |  |  |  | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember | 0 fnlc_CommercialAndMunicipalRiskRatedLoansReceivable / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_DoubtfulMember |
Municipal | Specific Reserves Evaluated Individually for Impairment |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |
Municipal | General Reserves Based on Historical Loss Experience |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |
Municipal | Reserve for Qualitative Factors |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 15,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 15,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 15,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 15,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |
Total Allowance for Loan Losses | 15,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 15,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 15,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 15,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 15,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 15,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 15,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 15,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 15,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 15,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 15,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 15,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |
Municipal | Unallocated Reserves |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_MunicipalMember |
Residential Term |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Allowance for Loans Evaluated Individually for Impairment | 519,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 404,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 519,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 404,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 395,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember
Allowance for Loans Evaluated Collectively for Impairment | 666,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 695,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 666,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 695,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 714,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember
Total Allowance for Loan Losses | 1,185,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 1,099,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 1,185,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 1,099,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 1,109,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember
Total Allowance for Loan Losses | 1,185,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 1,099,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 1,185,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 1,099,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 1,109,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Beginning balance |  |  |  | 1,099,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 1,109,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 1,099,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 1,109,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 1,159,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember
Chargeoffs |  |  |  |  |  |  |  |  | 699,000 us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 1,118,000 us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 1,911,000 us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember
Recoveries |  |  |  |  |  |  |  |  | 36,000 us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 103,000 us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 110,000 us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember
Provision for loan losses |  |  |  |  |  |  |  |  | 749,000 us-gaap_ProvisionForLoanAndLeaseLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 1,005,000 us-gaap_ProvisionForLoanAndLeaseLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 1,751,000 us-gaap_ProvisionForLoanAndLeaseLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember
Ending balance | 1,185,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 1,099,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 1,185,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 1,099,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 1,109,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember
Ending balance specifically evaluated for impairment | 519,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 404,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 519,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 404,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 395,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember
Ending balance collectively evaluated for impairment | 666,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 695,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 666,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 695,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 714,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember
Related loan balances |  |  |  |  |  |  |  |  |  |  |
Ending balance | 384,032,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 377,218,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 384,032,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 377,218,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 379,447,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember
Ending balance specifically evaluated for impairment | 16,123,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 17,786,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 16,123,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 17,786,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 19,444,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember
Ending balance collectively evaluated for impairment | 367,909,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 359,432,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 367,909,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 359,432,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 360,003,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 1,185,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 1,099,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 1,185,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 1,099,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 1,109,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember
Residential Term | Specific Reserves Evaluated Individually for Impairment |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 519,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 404,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 519,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 404,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |
Total Allowance for Loan Losses | 519,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 404,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 519,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 404,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 519,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 404,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 519,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 404,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 519,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 404,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 519,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 404,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |
Residential Term | General Reserves Based on Historical Loss Experience |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 297,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 342,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 297,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 342,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |
Total Allowance for Loan Losses | 297,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 342,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 297,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 342,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 297,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 342,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 297,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 342,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 297,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 342,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 297,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 342,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |
Residential Term | Reserve for Qualitative Factors |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 369,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 353,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 369,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 353,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |
Total Allowance for Loan Losses | 369,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 353,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 369,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 353,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 369,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 353,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 369,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 353,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 369,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 353,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 369,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 353,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |
Residential Term | Unallocated Reserves |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialTermMember |
Residential Construction |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Allowance for Loans Evaluated Individually for Impairment | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember
Allowance for Loans Evaluated Collectively for Impairment | 20,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 21,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 20,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 21,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 11,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember
Total Allowance for Loan Losses | 20,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 21,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 20,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 21,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 11,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember
Total Allowance for Loan Losses | 20,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 21,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 20,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 21,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 11,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Beginning balance |  |  |  | 21,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 11,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 21,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 11,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 255,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember
Chargeoffs |  |  |  |  |  |  |  |  | 0 us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 0 us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 389,000 us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember
Recoveries |  |  |  |  |  |  |  |  | 25,000 us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 0 us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 54,000 us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember
Provision for loan losses |  |  |  |  |  |  |  |  | (26,000)us-gaap_ProvisionForLoanAndLeaseLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 10,000 us-gaap_ProvisionForLoanAndLeaseLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 91,000 us-gaap_ProvisionForLoanAndLeaseLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember
Ending balance | 20,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 21,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 20,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 21,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 11,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember
Ending balance specifically evaluated for impairment | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember
Ending balance collectively evaluated for impairment | 20,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 21,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 20,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 21,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 11,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember
Related loan balances |  |  |  |  |  |  |  |  |  |  |
Ending balance | 12,160,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 11,803,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 12,160,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 11,803,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 6,459,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember
Ending balance specifically evaluated for impairment | 0 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 0 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 0 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 0 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 0 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember
Ending balance collectively evaluated for impairment | 12,160,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 11,803,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 12,160,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 11,803,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 6,459,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 20,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 21,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 20,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 21,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 11,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember
Residential Construction | Specific Reserves Evaluated Individually for Impairment |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |
Residential Construction | General Reserves Based on Historical Loss Experience |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 9,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 10,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 9,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 10,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |
Total Allowance for Loan Losses | 9,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 10,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 9,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 10,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 9,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 10,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 9,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 10,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 9,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 10,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 9,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 10,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |
Residential Construction | Reserve for Qualitative Factors |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 11,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 11,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 11,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 11,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |
Total Allowance for Loan Losses | 11,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 11,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 11,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 11,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 11,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 11,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 11,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 11,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 11,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 11,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 11,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 11,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |
Residential Construction | Unallocated Reserves |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fnlc_ResidentialConstructionMember |
Home equity line of credit |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Allowance for Loans Evaluated Individually for Impairment | 396,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 54,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 396,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 54,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember
Allowance for Loans Evaluated Collectively for Impairment | 664,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 621,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 664,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 621,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 654,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember
Total Allowance for Loan Losses | 1,060,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 675,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 1,060,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 675,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 654,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember
Total Allowance for Loan Losses | 1,060,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 675,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 1,060,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 675,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 654,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Beginning balance |  |  |  | 675,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 654,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 675,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 654,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 595,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember
Chargeoffs |  |  |  |  |  |  |  |  | 153,000 us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 611,000 us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 688,000 us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember
Recoveries |  |  |  |  |  |  |  |  | 16,000 us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 24,000 us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 1,000 us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember
Provision for loan losses |  |  |  |  |  |  |  |  | 522,000 us-gaap_ProvisionForLoanAndLeaseLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 608,000 us-gaap_ProvisionForLoanAndLeaseLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 746,000 us-gaap_ProvisionForLoanAndLeaseLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember
Ending balance | 1,060,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 675,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 1,060,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 675,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 654,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember
Ending balance specifically evaluated for impairment | 396,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 54,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 396,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 54,000 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember
Ending balance collectively evaluated for impairment | 664,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 621,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 664,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 621,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 654,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember
Related loan balances |  |  |  |  |  |  |  |  |  |  |
Ending balance | 103,521,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 91,549,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 103,521,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 91,549,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 99,082,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember
Ending balance specifically evaluated for impairment | 2,087,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 1,648,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 2,087,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 1,648,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 1,311,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember
Ending balance collectively evaluated for impairment | 101,434,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 89,901,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 101,434,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 89,901,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 97,771,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 1,060,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 675,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 1,060,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 675,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 654,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember
Home equity line of credit | Specific Reserves Evaluated Individually for Impairment |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 396,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 54,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 396,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 54,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |
Total Allowance for Loan Losses | 396,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 54,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 396,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 54,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 396,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 54,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 396,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 54,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 396,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 54,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 396,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 54,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |
Home equity line of credit | General Reserves Based on Historical Loss Experience |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 376,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 343,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 376,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 343,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |
Total Allowance for Loan Losses | 376,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 343,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 376,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 343,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 376,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 343,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 376,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 343,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 376,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 343,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 376,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 343,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |
Home equity line of credit | Reserve for Qualitative Factors |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 288,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 278,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 288,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 278,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |
Total Allowance for Loan Losses | 288,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 278,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 288,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 278,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 288,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 278,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 288,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 278,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 288,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 278,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 288,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 278,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |
Home equity line of credit | Unallocated Reserves |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |
Consumer |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Allowance for Loans Evaluated Individually for Impairment | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember
Allowance for Loans Evaluated Collectively for Impairment | 542,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 573,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 542,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 573,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 592,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember
Total Allowance for Loan Losses | 542,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 573,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 542,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 573,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 592,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember
Total Allowance for Loan Losses | 542,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 573,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 542,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 573,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 592,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Beginning balance |  |  |  | 573,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 592,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 573,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 592,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 584,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember
Chargeoffs |  |  |  |  |  |  |  |  | 449,000 us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 430,000 us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 555,000 us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember
Recoveries |  |  |  |  |  |  |  |  | 196,000 us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 183,000 us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 208,000 us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember
Provision for loan losses |  |  |  |  |  |  |  |  | 222,000 us-gaap_ProvisionForLoanAndLeaseLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 228,000 us-gaap_ProvisionForLoanAndLeaseLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 355,000 us-gaap_ProvisionForLoanAndLeaseLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember
Ending balance | 542,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 573,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 542,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 573,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 592,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember
Ending balance specifically evaluated for impairment | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember
Ending balance collectively evaluated for impairment | 542,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 573,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 542,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 573,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 592,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember
Related loan balances |  |  |  |  |  |  |  |  |  |  |
Ending balance | 19,653,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 15,066,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 19,653,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 15,066,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 14,657,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember
Ending balance specifically evaluated for impairment | 26,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 0 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 26,000 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 0 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 0 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember
Ending balance collectively evaluated for impairment | 19,627,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 15,066,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 19,627,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 15,066,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 14,657,000 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 542,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 573,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 542,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 573,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 592,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember
Consumer | Specific Reserves Evaluated Individually for Impairment |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |
Consumer | General Reserves Based on Historical Loss Experience |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 346,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 382,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 346,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 382,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |
Total Allowance for Loan Losses | 346,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 382,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 346,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 382,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 346,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 382,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 346,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 382,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 346,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 382,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 346,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 382,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |
Consumer | Reserve for Qualitative Factors |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 196,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 191,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 196,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 191,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |
Total Allowance for Loan Losses | 196,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 191,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 196,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 191,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 196,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 191,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 196,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 191,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 196,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 191,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 196,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 191,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |
Consumer | Unallocated Reserves |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ConsumerPortfolioSegmentMember |
Unallocated Financing Receivables |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Allowance for Loans Evaluated Individually for Impairment | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember
Allowance for Loans Evaluated Collectively for Impairment | 1,662,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 1,678,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 1,662,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 1,678,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 842,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember
Total Allowance for Loan Losses | 1,662,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 1,678,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 1,662,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 1,678,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 842,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember
Total Allowance for Loan Losses | 1,662,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 1,678,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 1,662,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 1,678,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 842,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Beginning balance |  |  |  | 1,678,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 842,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 1,678,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 842,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 2,008,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember
Chargeoffs |  |  |  |  |  |  |  |  | 0 us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 0 us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 0 us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember
Recoveries |  |  |  |  |  |  |  |  | 0 us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 0 us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 0 us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember
Provision for loan losses |  |  |  |  |  |  |  |  | (16,000)us-gaap_ProvisionForLoanAndLeaseLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 836,000 us-gaap_ProvisionForLoanAndLeaseLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | (1,166,000)us-gaap_ProvisionForLoanAndLeaseLosses / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember
Ending balance | 1,662,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 1,678,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 1,662,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 1,678,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 842,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember
Ending balance specifically evaluated for impairment | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 0 us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember
Ending balance collectively evaluated for impairment | 1,662,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 1,678,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 1,662,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 1,678,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 842,000 us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember
Related loan balances |  |  |  |  |  |  |  |  |  |  |
Ending balance | 0 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 0 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 0 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember
Ending balance specifically evaluated for impairment | 0 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 0 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 0 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 0 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 0 us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember
Ending balance collectively evaluated for impairment | 0 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 0 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 0 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 0 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 0 us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 1,662,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 1,678,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 1,662,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 1,678,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 842,000 us-gaap_LoansAndLeasesReceivableAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember
Unallocated Financing Receivables | Specific Reserves Evaluated Individually for Impairment |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_SpecificReservesEvaluatedIndividuallyForImpairmentMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |
Unallocated Financing Receivables | General Reserves Based on Historical Loss Experience |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_GeneralReservesBasedOnHistoricalLossExperienceMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |
Unallocated Financing Receivables | Reserve for Qualitative Factors |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 0 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_ReserveForQualitativeFactorsMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |
Unallocated Financing Receivables | Unallocated Reserves |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 1,662,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 1,678,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 1,662,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 1,678,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |
Total Allowance for Loan Losses | 1,662,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 1,678,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 1,662,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 1,678,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |
Allowance for loan losses |  |  |  |  |  |  |  |  |  |  |
Ending balance | 1,662,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 1,678,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 1,662,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 1,678,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Total Allowance for Loan Losses | 1,662,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 1,678,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |  |  |  | 1,662,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember | 1,678,000 us-gaap_LoansAndLeasesReceivableAllowance / fnlc_FinancingReceivableInformationByTypeOfReserveAxis = fnlc_UnallocatedReservesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_UnallocatedFinancingReceivablesMember |
Minimum |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk Based Ratios, Weighted-Average Required Reserve as Percent of Total Loans |  |  |  |  |  |  |  |  |  | 0.88%fnlc_RiskBasedRatiosWeightedAverageRequiredReserveasPercentofTotalLoans / us-gaap_RangeAxis = us-gaap_MinimumMember |
Regulatory Capital Requirements, Estimated Required Reserve |  |  |  |  |  |  |  |  |  | 8,700,000.0 fnlc_RegulatoryCapitalRequirementsEstimatedRequiredReserve / us-gaap_RangeAxis = us-gaap_MinimumMember |
Maximum |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk Based Ratios, Weighted-Average Required Reserve as Percent of Total Loans |  |  |  |  |  |  |  |  |  | 1.60%fnlc_RiskBasedRatiosWeightedAverageRequiredReserveasPercentofTotalLoans / us-gaap_RangeAxis = us-gaap_MaximumMember |
Regulatory Capital Requirements, Estimated Required Reserve |  |  |  |  |  |  |  |  |  | $ 13,900,000.0 fnlc_RegulatoryCapitalRequirementsEstimatedRequiredReserve / us-gaap_RangeAxis = us-gaap_MaximumMember |

X
- Definition Allowance for Loan and Lease Losses, Related Loans, Percentage + References No definition available. + Details
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Balance Type: | na
Period Type: | duration

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- Definition Allowance for Loan and Lease Losses, Related Loans, Period Increase (Decrease) + References No definition available. + Details
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Namespace Prefix: | fnlc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition Allowance for Loan Losses of Total Loans, Percentage + References No definition available. + Details
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Namespace Prefix: | fnlc_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- Definition AverageLoanGrowth + References No definition available. + Details
Name: | fnlc_AverageLoanGrowth
Namespace Prefix: | fnlc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition The high maximum percentage of loan to value for consumer loans based on purchase price of the collateral. + References No definition available. + Details
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Namespace Prefix: | fnlc_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- Definition The low maximum percentage of loan to value for consumer loans based on purchase price of the collateral. + References No definition available. + Details
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Namespace Prefix: | fnlc_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- Definition Loans subject to review and validation annually by independent consulting firm as well internal credit review function. + References No definition available. + Details
Name: | fnlc_CommercialAndMunicipalRiskRatedLoansReceivable
Namespace Prefix: | fnlc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The maximum percentage of loan to value for commercial real estate loans based on current appraisal information. + References No definition available. + Details
Name: | fnlc_CommercialRealEstateLoansMaximumLoanToValue
Namespace Prefix: | fnlc_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- Definition The regulatory maximum allowed ratio of loan portfolio to Company capital for construction and non-owner-occupied commercial real estate. + References No definition available. + Details
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Namespace Prefix: | fnlc_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- Definition The actual ratio of loan amount to Company capital for construction and non-owner-occupied commercial real estate. + References No definition available. + Details
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Namespace Prefix: | fnlc_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- Definition The regulatory maximum allowed ratio of loan portfolio to Company capital for construction loans. + References No definition available. + Details
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Namespace Prefix: | fnlc_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- Definition The ratio of loan portfolio to Company capital for construction loans . + References No definition available. + Details
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Namespace Prefix: | fnlc_
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