| **Investment Securities Amortized Cost and Estimated Fair Value of Available for Sale Securities (Details) (USD $)In Thousands, unless otherwise specified** | Jun. 30, 2014 | Dec. 31, 2013 | Jun. 30, 2013 |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------|---------------|---------------|
| **Schedule of Available-for-sale Securities [Line Items]**                                                                                                   |          |          |          |
| Amortized Cost                                                                                                                                               | $ 301,501     | $ 315,963     | $ 293,016     |
| Unrealized Gains                                                                                                                                             | 6,455         | 2,966         | 4,032         |
| Unrealized Losses                                                                                                                                            | (4,076)       | (13,105)      | (9,313)       |
| Fair Value (Estimated)                                                                                                                                       | 303,880       | 305,824       | 287,735       |
| Collateralized Mortgage Backed Securities [Member]                                                                                                           |          |          |          |
| **Schedule of Available-for-sale Securities [Line Items]**                                                                                                   |          |          |          |
| Amortized Cost                                                                                                                                               | 165,978       | 180,109       | 157,023       |
| Unrealized Gains                                                                                                                                             | 2,417         | 1,392         | 2,014         |
| Unrealized Losses                                                                                                                                            | (1,692)       | (3,772)       | (1,513)       |
| Fair Value (Estimated)                                                                                                                                       | 166,703       | 177,729       | 157,524       |
| US States and Political Subdivisions Debt Securities [Member]                                                                                                |          |          |          |
| **Schedule of Available-for-sale Securities [Line Items]**                                                                                                   |          |          |          |
| Amortized Cost                                                                                                                                               | 133,327       | 134,188       | 134,376       |
| Unrealized Gains                                                                                                                                             | 3,951         | 1,458         | 1,955         |
| Unrealized Losses                                                                                                                                            | (2,383)       | (9,331)       | (7,792)       |
| Fair Value (Estimated)                                                                                                                                       | 134,895       | 126,315       | 128,539       |
| Equity Securities [Member]                                                                                                                                   |          |          |          |
| **Schedule of Available-for-sale Securities [Line Items]**                                                                                                   |          |          |          |
| Amortized Cost                                                                                                                                               | 2,196         | 1,666         | 1,617         |
| Unrealized Gains                                                                                                                                             | 87            | 116           | 63            |
| Unrealized Losses                                                                                                                                            | (1)           | (2)           | (8)           |
| Fair Value (Estimated)                                                                                                                                       | $ 2,282       | $ 1,780       | $ 1,672       |

| X                                                                                                                                                                                                                                                                                                                                                                                                                            |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                           |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.
+ References
No definition available.
+ Details**Name:**fnlc_AvailableforSaleSecuritiesAccumulatedGrossUnrealizedLossbeforeTax**Namespace Prefix:**fnlc_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 25 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=28360136&loc=d3e22054-111558Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.2) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682
+ Details**Name:**us-gaap_AvailableForSaleSecuritiesAmortizedCost**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                 |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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