Name:	fnlc_FinancingReceivableLoansClassifiedAsTroubledDebtRestructuringsThatAreInvolvedInBankruptcy
Namespace Prefix:	fnlc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Financing Receivable Loans , Classified As Troubled Debt Restructurings That Were On Non Accrual Status

No definition available.

Name:	fnlc_FinancingReceivableLoansClassifiedAsTroubledDebtRestructuringsThatWereOnNonAccrualStatus
Namespace Prefix:	fnlc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The number of financing receivables that have been modified by troubled debt restructurings during the current period.

No definition available.

Name:	fnlc_FinancingReceivableModificationsNumberOfContractsDuringPeriod
Namespace Prefix:	fnlc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Financing Receivable Modifications Number Of Contracts Greater Than 30 Days Past Due

No definition available.

Name:	fnlc_FinancingReceivableModificationsNumberOfContractsGreaterThan30DaysPastDue
Namespace Prefix:	fnlc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

Financing Receivable, Modifications, Number Of Contracts Involved In Bankruptcy During Period

No definition available.

Name:	fnlc_FinancingReceivableModificationsNumberOfContractsInvolvedInBankruptcyDuringPeriod
Namespace Prefix:	fnlc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

The number of loans classified as troubled debt restructurings that were on non-accrual status as of the balance sheet date.

No definition available.

Name:	fnlc_FinancingReceivableNumberOfLoansClassifiedAsTroubledDebtRestructuringsThatWereOnNonAccrualStatus
Namespace Prefix:	fnlc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

Financing receivables that are greater than 30 days past due.

No definition available.

Name:	fnlc_FinancingReceivableRecordedInvestmentGreaterThan30DaysPastDue
Namespace Prefix:	fnlc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Loans Classified As Troubled Debt Restructurings That Are Involved In Foreclosure

No definition available.

Name:	fnlc_LoansClassifiedAsTroubledDebtRestructuringsThatAreInvolvedInForeclosure
Namespace Prefix:	fnlc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Mortgage Loans in Process of Foreclosure, Number

No definition available.

Name:	fnlc_MortgageLoansinProcessofForeclosureNumber
Namespace Prefix:	fnlc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

Number Of Days Past Due

No definition available.

Name:	fnlc_NumberOfDaysPastDue
Namespace Prefix:	fnlc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Reflects the break down of the gross carrying amount of all categories of loans and leases held in the portfolio, after deducting deferred income, but before deducting the allowance for losses on loans and leases as a percentage of total portfolio.

No definition available.

Name:	fnlc_PercentageOfFinancingReceivableByType
Namespace Prefix:	fnlc_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_AccountsNotesAndLoansReceivableLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Amount of the collateral pledged in support of federal home loan bank advances outstanding.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=123599511&loc=d3e64711-112823

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6479118&loc=d3e64650-112822

Name:	us-gaap_FederalHomeLoanBankAdvancesGeneralDebtObligationsDisclosuresCollateralPledged1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Number of financing receivables that have been modified by troubled debt restructurings.

Name:	us-gaap_FinancingReceivableModificationsNumberOfContracts2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Amount of financing receivable modified as troubled debt restructuring.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=123577603&loc=SL6953676-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=121585226&loc=d3e18845-111554

Name:	us-gaap_FinancingReceivableModificationsRecordedInvestment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Number of financing receivable contracts modified as troubled debt restructuring within previous 12 months, with subsequent payment default.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=123577603&loc=SL6953682-111524

Name:	us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Amount of deferred interest and fee income, unamortized costs incurred to originate loans and leases, unamortized loan commitments and loan syndication fees, and premiums over or discounts from face amounts of acquired loans. Excludes amounts for loans and leases covered under loss sharing agreements.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7)
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 30
-Section 50
-Paragraph 4
-Subparagraph (a)(4)
-URI http://asc.fasb.org/extlink&oid=123392090&loc=d3e45377-112738

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=123577603&loc=d3e5074-111524

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 20
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=84159169&loc=d3e10152-111534

Name:	us-gaap_LoansAndLeasesReceivableDeferredIncome
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Carrying amount as of the balance sheet date of loans that have been pledged as collateral for borrowings. If the secured party has the right by contract or custom to sell or re-pledge the collateral, then the debtor reclassifies that asset and report that asset in its statement of financial position separately from other assets not so encumbered.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66007379&loc=d3e113888-111728

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=123577603&loc=d3e5086-111524

Name:	us-gaap_LoansPledgedAsCollateral
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Recorded investment of consumer mortgage loan receivables secured by residential real estate properties for which formal foreclosure proceedings are in process.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 35
-URI http://asc.fasb.org/extlink&oid=123577603&loc=SL49126937-111524