Fair Value - Assets and Liabilities at Fair Value (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 13,855	$ 13,057	$ 13,894	$ 16,570
Interest bearing deposits in other banks	336us-gaap_InterestBearingDepositsInBanks	3,559us-gaap_InterestBearingDepositsInBanks	2,935us-gaap_InterestBearingDepositsInBanks
Securities available for sale	156,317us-gaap_AvailableForSaleSecurities	185,261us-gaap_AvailableForSaleSecurities	305,700us-gaap_AvailableForSaleSecurities
Securities to be held to maturity	262,455us-gaap_HeldToMaturitySecurities	275,919us-gaap_HeldToMaturitySecurities	182,853us-gaap_HeldToMaturitySecurities
Securities to be held to maturity	267,247	279,704	176,562
Restricted equity securities	13,912fnlc_RestrictedEquitySecuritiesAtCost	13,912fnlc_RestrictedEquitySecuritiesAtCost	13,912fnlc_RestrictedEquitySecuritiesAtCost
Loans held for sale	0	0	56
Municipal	26,257	20,406	17,772
Home equity line of credit	102,826fnlc_HomeEquityLineOfCredit	102,258fnlc_HomeEquityLineOfCredit	91,362fnlc_HomeEquityLineOfCredit
Consumer	19,086	19,007	14,321
Total loans	928,973	907,220	857,259
Mortgage servicing rights	1,003us-gaap_ServicingAssetAtAmortizedValue	1,086us-gaap_ServicingAssetAtAmortizedValue	1,129us-gaap_ServicingAssetAtAmortizedValue
Mortgage servicing rights	1,746us-gaap_ServicingAssetAtFairValueAmount	2,088us-gaap_ServicingAssetAtFairValueAmount	2,114us-gaap_ServicingAssetAtFairValueAmount
Accrued interest receivable	5,724	4,748	5,962
Demand deposits	100,939us-gaap_DemandDepositAccounts	113,133us-gaap_DemandDepositAccounts	94,260us-gaap_DemandDepositAccounts
NOW deposits	199,099	199,977	158,278
Money market deposits	101,292us-gaap_DepositsMoneyMarketDeposits	98,607us-gaap_DepositsMoneyMarketDeposits	89,382us-gaap_DepositsMoneyMarketDeposits
Savings deposits	167,338us-gaap_DepositsSavingsDeposits	165,601us-gaap_DepositsSavingsDeposits	149,076us-gaap_DepositsSavingsDeposits
Local certificates of deposit	199,553fnlc_LocalCertificatesofDeposit	205,072fnlc_LocalCertificatesofDeposit	224,552fnlc_LocalCertificatesofDeposit
National certificates of deposit	198,604fnlc_NationalCertificatesOfDeposit	242,429fnlc_NationalCertificatesOfDeposit	330,422fnlc_NationalCertificatesOfDeposit
Total deposits	966,825us-gaap_Deposits	1,024,819us-gaap_Deposits	1,045,970us-gaap_Deposits
Repurchase agreements	85,657	74,725	83,372
Federal Home Loan Bank advances	226,919	205,191	170,147
Total borrowed funds	312,576us-gaap_DebtAndCapitalLeaseObligations	279,916us-gaap_DebtAndCapitalLeaseObligations	253,519us-gaap_DebtAndCapitalLeaseObligations
Accrued interest payable	564	521	607
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	13,855	13,057	13,894
Interest bearing deposits in other banks	336	3,559	2,935
Securities available for sale	0	0	0
Securities to be held to maturity	0	0	0
Restricted equity securities	0	0	0
Loans held for sale			0
Municipal	0	0	0
Home equity line of credit	0	0	0
Consumer	0	0	0
Total loans	0	0	0
Mortgage servicing rights	0	0	0
Accrued interest receivable	0	0	0
Demand deposits	0	0	0
NOW deposits	0	0	0
Money market deposits	0	0	0
Savings deposits	0	0	0
Local certificates of deposit	0	0	0
National certificates of deposit	0	0	0
Total deposits	0	0	0
Repurchase agreements	0	0	0
Federal Home Loan Bank advances	0	0	0
Total borrowed funds	0	0	0
Accrued interest payable	0	0	0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0	0
Interest bearing deposits in other banks	0	0	0
Securities available for sale	156,317	185,261	305,700
Securities to be held to maturity	267,247	279,704	176,562
Restricted equity securities	13,912	13,912	13,912
Loans held for sale			56
Municipal	0	0	0
Home equity line of credit	228	488	59
Consumer	0	0	0
Total loans	1,439	1,909	2,327
Mortgage servicing rights	1,746	2,088	2,114
Accrued interest receivable	5,724	4,748	5,962
Demand deposits	99,935	109,973	87,904
NOW deposits	189,139	186,490	140,824
Money market deposits	87,816	83,837	72,560
Savings deposits	151,345	146,936	126,637
Local certificates of deposit	200,506	205,360	226,091
National certificates of deposit	198,846	242,824	332,069
Total deposits	927,587	975,420	986,085
Repurchase agreements	81,693	70,783	83,372
Federal Home Loan Bank advances	230,230	208,259	174,646
Total borrowed funds	311,923	279,042	258,018
Accrued interest payable	564	521	607
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0	0
Interest bearing deposits in other banks	0	0	0
Securities available for sale	0	0	0
Securities to be held to maturity	0	0	0
Restricted equity securities	0	0	0
Loans held for sale			0
Municipal	26,844	20,833	18,089
Home equity line of credit	102,074	101,245	91,016
Consumer	19,259	19,207	14,650
Total loans	932,717	910,146	858,642
Mortgage servicing rights	0	0	0
Accrued interest receivable	0	0	0
Demand deposits	0	0	0
NOW deposits	0	0	0
Money market deposits	0	0	0
Savings deposits	0	0	0
Local certificates of deposit	0	0	0
National certificates of deposit	0	0	0
Total deposits	0	0	0
Repurchase agreements	0	0	0
Federal Home Loan Bank advances	0	0	0
Total borrowed funds	0	0	0
Accrued interest payable	0	0	0
Commercial real estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial	238,218	238,104	234,848
Commercial real estate \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial	0	0	0
Commercial real estate \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial	184	431	672
Commercial real estate \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial	236,156	235,937	232,633
Commercial construction
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial	33,698	29,951	20,986
Commercial construction \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial	0	0	0
Commercial construction \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial	0	0	0
Commercial construction \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial	33,432	29,733	20,848
Commercial other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial	113,363	102,738	94,618
Commercial other \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial	0	0	0
Commercial other \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial	9	0	199
Commercial other \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial	113,400	102,858	94,689
Residential term
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Residential	382,517	382,620	371,018
Residential term \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Residential	0	0	0
Residential term \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Residential	1,018	990	1,397
Residential term \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Residential	388,564	388,210	374,405
Residential construction
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Residential	13,008	12,136	12,334
Residential construction \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Residential	0	0	0
Residential construction \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Residential	0	0	0
Residential construction \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Residential	12,988	12,123	12,312
Total Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	13,855	13,057	13,894
Interest bearing deposits in other banks	336	3,559	2,935
Securities available for sale	156,317	185,261	305,700
Securities to be held to maturity	267,247	279,704	176,562
Restricted equity securities	13,912	13,912	13,912
Loans held for sale			56
Municipal	26,844	20,833	18,089
Home equity line of credit	102,302	101,733	91,075
Consumer	19,259	19,207	14,650
Total loans	934,156	912,055	860,969
Mortgage servicing rights	1,746	2,088	2,114
Accrued interest receivable	5,724	4,748	5,962
Demand deposits	99,935	109,973	87,904
NOW deposits	189,139	186,490	140,824
Money market deposits	87,816	83,837	72,560
Savings deposits	151,345	146,936	126,637
Local certificates of deposit	200,506	205,360	226,091
National certificates of deposit	198,846	242,824	332,069
Total deposits	927,587	975,420	986,085
Repurchase agreements	81,693	70,783	83,372
Federal Home Loan Bank advances	230,230	208,259	174,646
Total borrowed funds	311,923	279,042	258,018
Accrued interest payable	564	521	607
Total Fair Value \| Commercial real estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial	236,340	236,368	233,305
Total Fair Value \| Commercial construction
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial	33,432	29,733	20,848
Total Fair Value \| Commercial other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial	113,409	102,858	94,888
Total Fair Value \| Residential term
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Residential	389,582	389,200	375,802
Total Fair Value \| Residential construction
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Residential	$ 12,988	$ 12,123	$ 12,312

Represents the portion of the balance sheet assertion valued at fair value whether such amount is presented as a separate caption or as a parenthetical disclosure. Element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. May be used in both the balance sheet and disclosure in the same submission. This item represents the amount shown on an entity's books for accrued interest receivable.

No definition available.