| **Mortgage Servicing Rights Included in Other Assets (Details) - USD ($) $ in Thousands** | Jun. 30, 2016 | Dec. 31, 2015 | Jun. 30, 2015 |
|-------------------------------------------------------------------------------------------|---------------|---------------|---------------|
| **Transfers and Servicing [Abstract]**                                                    |          |          |          |
| Mortgage servicing rights                                                                 | $ 5,520       | $ 5,747       | $ 6,266       |
| Accumulated amortization                                                                  | (4,433)       | (4,619)       | (5,170)       |
| Impairment reserve                                                                        | (139)         | (35)          | (25)          |
| Total Servicing asset at fair value                                                       | $ 948         | $ 1,093       | $ 1,071       |

| X                                                                                                                                                                                                                                                                                                                                                          |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The cumulative amount of amortization for mortgage servicing rights that has been recognized in the income statement.
+ References
No definition available.
+ Details**Name:**fnlc_AccumulatedAmortizationMortgageServicingRights**Namespace Prefix:**fnlc_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                           |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Gross amount, as of the balance sheet date, of mortgage servicing rights.
+ References
No definition available.
+ Details**Name:**fnlc_MortgageServicingRightsGross**Namespace Prefix:**fnlc_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
A reserve for the amount of expected decrease in the value of mortgage servicing rights which cannot be physically measured.
+ References
No definition available.
+ Details**Name:**fnlc_ReserveForImpairmentOfMortgageServicingRights**Namespace Prefix:**fnlc_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Fair value of contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 50 -Section 50 -Paragraph 4 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=68078379&loc=d3e122739-111746Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=7516967&loc=d3e66267-113978
+ Details**Name:**us-gaap_ServicingAssetAtAmortizedValueFairValue**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                       |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - References
No definition available.
+ Details**Name:**us-gaap_TransfersAndServicingAbstract**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |