| **Investment Securities (Tables)**                                              | 3 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
|---------------------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
||
| **Investments Securities [Abstract]**                                           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
| Schedule of Available For Sale, Held-to-Maturity, and Non-Marketable Securities | The following table summarizes the amortized cost and estimated fair value of investment securities at March 31, 2012:   Amortized  Unrealized  Unrealized  Fair Value    Cost  Gains  Losses  (Estimated) Securities available for sale            U.S. Treasury and agency $-  $-  $-  $- Mortgage-backed securities  226,671,000   5,805,000   (361,000)  232,115,000 State and political subdivisions  77,672,000   5,540,000   (50,000)  83,162,000 Corporate securities  -   -   -   - Other equity securities  1,863,000   44,000   (73,000)  1,834,000    $306,206,000  $11,389,000  $(484,000) $317,111,000 Securities to be held to maturity                U.S. Treasury and agency $39,694,000  $37,000  $(435,000) $39,296,000 Mortgage-backed securities  52,185,000   3,638,000   -   55,823,000 State and political subdivisions  45,427,000   3,941,000   (154,000)  49,214,000 Corporate securities  300,000   -   -   300,000    $137,606,000  $7,616,000  $(589,000) $144,633,000 Non-marketable securities                Federal Home Loan Bank Stock $13,412,000  $-  $-  $13,412,000 Federal Reserve Bank Stock  1,411,000   -   -   1,411,000    $14,823,000  $-  $-  $14,823,000 The following table summarizes the amortized cost and estimated fair value of investment securities at December 31, 2011:   Amortized  Unrealized  Unrealized  Fair Value    Cost  Gains  Losses  (Estimated) Securities available for sale            U.S. Treasury and agency $-  $-  $-  $- Mortgage-backed securities  191,924,000   6,486,000   (178,000)  198,232,000 State and political subdivisions  80,259,000   5,484,000   (17,000)  85,726,000 Corporate securities  1,098,000   -   (287,000)  811,000 Other equity securities  1,535,000   37,000   (139,000)  1,433,000    $274,816,000  $12,007,000  $(621,000) $286,202,000 Securities to be held to maturity                U.S. Treasury and agency $19,390,000  $132,000  $-  $19,522,000 Mortgage-backed securities  56,800,000   3,900,000   (3,000)  60,697,000 State and political subdivisions  46,171,000   4,159,000   (172,000)  50,158,000 Corporate securities  300,000   -   -   300,000    $122,661,000  $8,191,000  $(175,000) $130,677,000 Non-marketable securities                Federal Home Loan Bank Stock $14,032,000  $-  $-  $14,032,000 Federal Reserve Bank Stock  1,411,000   -   -   1,411,000    $15,443,000  $-  $-  $15,443,000 The following table summarizes the amortized cost and estimated fair value of investment securities at March 31, 2011:   Amortized  Unrealized  Unrealized  Fair Value    Cost  Gains  Losses  (Estimated) Securities available for sale            U.S. Treasury and agency $15,352,000  $591,000  $-  $15,943,000 Mortgage-backed securities  255,703,000   1,138,000   (3,731,000)  253,110,000 State and political subdivisions  55,040,000   577,000   (536,000)  55,081,000 Corporate securities  1,108,000   -   (185,000)  923,000 Other equity securities  385,000   18,000   (9,000)  394,000    $327,588,000  $2,324,000  $(4,461,000) $325,451,000 Securities to be held to maturity                U.S. Treasury and agency $2,936,000  $-  $(292,000) $2,644,000 Mortgage-backed securities  59,063,000   3,348,000   (76,000)  62,335,000 State and political subdivisions  47,787,000   1,641,000   (506,000)  48,922,000 Corporate securities  150,000   -   -   150,000    $109,936,000  $4,989,000  $(874,000) $114,051,000 Non-marketable securities                Federal Home Loan Bank Stock $14,032,000  $-  $-  $14,032,000 Federal Reserve Bank Stock  1,411,000   -   -   1,411,000    $15,443,000  $-  $-  $15,443,000  |
| Contractual Maturities of Investment Securities                                 | The following table summarizes the contractual maturities of investment securities at March 31, 2012:   Securities available for sale  Securities to be held to maturity    AmortizedCost  Fair Value (Estimated)  AmortizedCost  Fair Value (Estimated) Due in 1 year or less $5,894,000  $5,948,000  $4,663,000  $4,710,000 Due in 1 to 5 years  59,887,000   60,971,000   12,173,000   12,940,000 Due in 5 to 10 years  13,014,000   13,442,000   35,563,000   38,100,000 Due after 10 years  225,548,000   234,916,000   85,207,000   88,883,000 Equity securities  1,863,000   1,834,000   -   -    $306,206,000  $317,111,000  $137,606,000  $144,633,000 The following table summarizes the contractual maturities of investment securities at December 31, 2011:   Securities available for sale  Securities to be held to maturity    AmortizedCost  Fair Value (Estimated)  AmortizedCost  Fair Value (Estimated) Due in 1 year or less $6,617,000  $6,773,000  $5,179,000  $5,227,000 Due in 1 to 5 years  18,792,000   19,473,000   10,085,000   10,654,000 Due in 5 to 10 years  23,219,000   24,065,000   23,027,000   24,694,000 Due after 10 years  224,653,000   234,458,000   84,370,000   90,102,000 Equity securities  1,535,000   1,433,000   -   -    $274,816,000  $286,202,000  $122,661,000  $130,677,000 The following table summarizes the contractual maturities of investment securities at March 31, 2011:   Securities available for sale  Securities to be held to maturity    AmortizedCost  Fair Value (Estimated)  AmortizedCost  Fair Value (Estimated) Due in 1 year or less $212,000  $218,000  $1,072,000  $1,084,000 Due in 1 to 5 years  2,818,000   2,964,000   5,629,000   5,948,000 Due in 5 to 10 years  4,774,000   4,916,000   16,974,000   17,737,000 Due after 10 years  319,399,000   316,959,000   86,261,000   89,282,000 Equity securities  385,000   394,000   -   -    $327,588,000  $325,451,000  $109,936,000  $114,051,000                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
| Schedule of Securities Gains and Losses                                         | The following table shows securities gains and losses for the three months ended March 31, 2012 and 2011:   For the three months endedMarch 31, 2012  For the three months ended March 31, 2011 Proceeds from sales $10,943,000  $- Gross gains $812,000  $- Gross losses $(289,000) $- Net gain $523,000  $- Related income taxes $183,000  $-                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
| Schedule of Temporary Impairment Losses                                         | Information regarding securities temporarily impaired as of March 31, 2012 is summarized below:   Less than 12 months  12 months or more  Total    Fair  Unrealized  Fair  Unrealized  Fair  Unrealized    Value  Losses  Value  Losses  Value  Losses U.S. Treasury and agency $33,514,000  $(435,000) $-  $-  $33,514,000  $(435,000)Mortgage-backed securities  35,242,000   (280,000)  6,608,000   (81,000)  41,850,000   (361,000)State and political subdivisions  4,924,000   (204,000)  -   -   4,924,000   (204,000)Corporate securities  -   -   -   -   -   - Other equity securities  -   -   253,000   (73,000)  253,000   (73,000)   $73,680,000  $(919,000) $6,861,000  $(154,000) $80,541,000  $(1,073,000)As of December 31, 2011, there were 29 securities with unrealized losses held in the Company's portfolio. These securities were temporarily impaired as a result of changes in interest rates reducing their fair value, of which 11 had been temporarily impaired for 12 months or more. Information regarding securities temporarily impaired as of December 31, 2011 is summarized below:   Less than 12 months  12 months or more  Total    Fair  Unrealized  Fair  Unrealized  Fair  Unrealized    Value  Losses  Value  Losses  Value  Losses U.S. Treasury and agency $-  $-  $-  $-  $-  $- Mortgage-backed securities  12,489,000   (25,000)  6,780,000   (156,000)  19,269,000   (181,000)State and political subdivisions  1,984,000   (17,000)  1,667,000   (172,000)  3,651,000   (189,000)Corporate securities  -   -   811,000   (287,000)  811,000   (287,000)Other equity securities  154,000   (120,000)  34,000   (19,000)  188,000   (139,000)   $14,627,000  $(162,000) $9,292,000  $(634,000) $23,919,000  $(796,000)As of March 31, 2011, there were 104 securities with unrealized losses held in the Company's portfolio. These securities were temporarily impaired as a result of changes in interest rates reducing their fair market value, of which 12 had been temporarily impaired for 12 months or more. Information regarding securities temporarily impaired as of March 31, 2011 is summarized below:   Less than 12 months  12 months or more  Total    Fair  Unrealized  Fair  Unrealized  Fair  Unrealized    Value  Losses  Value  Losses  Value  Losses U.S. Treasury and agency $2,645,000  $(292,000) $-  $-  $2,645,000  $(292,000)Mortgage-backed securities  187,278,000   (3,471,000)  6,757,000   (336,000)  194,035,000   (3,807,000)State and political subdivisions  29,835,000   (659,000)  1,398,000   (383,000)  31,233,000   (1,042,000)Corporate securities  -   -   922,000   (185,000)  922,000   (185,000)Other equity securities  10,000   (2,000)  47,000   (7,000)  57,000   (9,000)   $219,768,000  $(4,424,000) $9,124,000  $(911,000) $228,892,000  $(5,335,000)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |

| X                                                                                                                                                                                                                                                                                                                                                                                                                    |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Tabular presentation of available for sale securities, held-to-maturity securities and non-marketable securities as of the balance sheet date.
+ References
No definition available.
+ Details**Name:**fnlc_ScheduleOfAvailableForSaleHeldToMaturityAndNonMarketableSecuritiesTableTextBlock**Namespace Prefix:**fnlc_**Data Type:**nonnum:textBlockItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                  |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Tabular disclosure of maturities of an entity's investments as well as any other information pertinent to the investments.
+ References
No definition available.
+ Details**Name:**us-gaap_InvestmentsClassifiedByContractualMaturityDateTableTextBlock**Namespace Prefix:**us-gaap_**Data Type:**nonnum:textBlockItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                              |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Tabular disclosure of the proceeds from sales of available-for-sale securities and the gross realized gains and gross realized losses that have been included in earnings as a result of those sales.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Topic 320 -SubTopic 10 -Publisher FASB -Number  -Article  -Subparagraph (a) -Name Accounting Standards Codification -Paragraph 9 -Section 50 -URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27357-111563
+ Details**Name:**us-gaap_ScheduleOfRealizedGainLossTableTextBlock**Namespace Prefix:**us-gaap_**Data Type:**nonnum:textBlockItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Tabular disclosure of investments in an unrealized loss position for which other-than-temporary impairments have not been recognized in earnings (including investments for which a portion of an other-than-temporary impairment has been recognized in other comprehensive income), including: (a) the aggregate related fair value of investments with unrealized losses, (b) the aggregate amount of unrealized losses (that is, the amount by which amortized cost basis exceeds fair value).
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Topic 320 -SubTopic 10 -Publisher FASB -Number  -Article  -Subparagraph  -Name Accounting Standards Codification -Paragraph 6 -Section 50 -URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27290-111563
+ Details**Name:**us-gaap_ScheduleOfTemporaryImpairmentLossesInvestmentsTableTextBlock**Namespace Prefix:**us-gaap_**Data Type:**nonnum:textBlockItemType**Balance Type:**na**Period Type:**duration |