| **Investment Securities**                              | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               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| **Investments, Debt and Equity Securities [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            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| Investment Securities                                  | Investment SecuritiesThe following tables summarize the amortized cost and estimated fair value of investment securities at December 31, 2013 and 2012: Amortized Unrealized Unrealized Fair ValueAs of December 31, 2013Cost Gains Losses (Estimated)Securities available for sale       Mortgage-backed securities$180,109,000 $1,392,000 $(3,772,000) $177,729,000State and political subdivisions134,188,000 1,458,000 (9,331,000) 126,315,000Other equity securities1,666,000 116,000 (2,000) 1,780,000 $315,963,000 $2,966,000 $(13,105,000) $305,824,000Securities to be held to maturity       U.S. Government-sponsored agencies$92,280,000 $1,000 $(12,757,000) $79,524,000Mortgage-backed securities35,712,000 1,440,000 (1,336,000) 35,816,000State and political subdivisions40,985,000 1,823,000 (112,000) 42,696,000Corporate securities300,000 — — 300,000 $169,277,000 $3,264,000 $(14,205,000) $158,336,000Restricted equity securities       Federal Home Loan Bank Stock$12,875,000 $— $— $12,875,000Federal Reserve Bank Stock1,037,000 — — 1,037,000 $13,912,000 $— $— $13,912,000 Amortized Unrealized Unrealized Fair ValueAs of December 31, 2012Cost Gains Losses (Estimated)Securities available for sale       Mortgage-backed securities$164,752,000 $4,636,000 $(295,000) $169,093,000State and political subdivisions113,069,000 8,074,000 (199,000) 120,944,000Other equity securities1,578,000 43,000 (44,000) 1,577,000 $279,399,000 $12,753,000 $(538,000) $291,614,000Securities to be held to maturity       U.S. Government-sponsored agencies$60,919,000 $242,000 $(182,000) $60,979,000Mortgage-backed securities39,193,000 2,850,000 (19,000) 42,024,000State and political subdivisions42,908,000 4,036,000 — 46,944,000Corporate securities300,000 — — 300,000 $143,320,000 $7,128,000 $(201,000) $150,247,000Restricted equity securities       Federal Home Loan Bank Stock$13,412,000 $— $— $13,412,000Federal Reserve Bank Stock1,036,000 — — 1,036,000 $14,448,000 $— $— $14,448,000The following table summarizes the contractual maturities of investment securities at December 31, 2013: Securities available for sale Securities to be held to maturity Amortized Cost Fair Value (Estimated) Amortized Cost Fair Value (Estimated)Due in 1 year or less$717,000 $721,000 $268,000 $273,000Due in 1 to 5 years20,547,000 20,636,000 6,420,000 6,790,000Due in 5 to 10 years16,114,000 16,267,000 33,442,000 33,828,000Due after 10 years276,919,000 266,420,000 129,147,000 117,445,000Equity securities1,666,000 1,780,000 — — $315,963,000 $305,824,000 $169,277,000 $158,336,000The following table summarizes the contractual maturities of investment securities at December 31, 2012: Securities available for sale Securities to be held to maturityIn thousands of dollarsAmortized Cost Fair Value (Estimated) Amortized Cost Fair Value (Estimated)Due in 1 year or less$18,761,000 $18,926,000 $3,754,000 $3,785,000Due in 1 to 5 years27,243,000 27,816,000 11,950,000 12,701,000Due in 5 to 10 years16,686,000 17,666,000 27,461,000 29,986,000Due after 10 years215,131,000 225,629,000 100,155,000 103,775,000Equity securities1,578,000 1,577,000 — — $279,399,000 $291,614,000 $143,320,000 $150,247,000At December 31, 2013, securities with a fair value of $147,074,000 were pledged to secure borrowings from the Federal Home Loan Bank of Boston, public deposits, repurchase agreements, and for other purposes as required by law. This compares to securities with a fair value of $154,817,000, as of December 31, 2012 pledged for the same purpose.Gains and losses on the sale of securities available for sale are computed by subtracting the amortized cost at the time of sale from the security's selling price, net of accrued interest to be received.The following table shows securities gains and losses for 2013, 2012 and 2011: 2013 2012 2011Proceeds from sales of securities$10,563,000 $26,437,000 $140,417,000Gross realized gains1,087,000 2,257,000 4,020,000Gross realized losses— (289,000) (727,000)Net gain$1,087,000 $1,968,000 $3,293,000Related income taxes$380,000 $689,000 $1,153,000Management reviews securities with unrealized losses for other than temporary impairment. As of December 31, 2013, there were 304 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 32 had been temporarily impaired for 12 months or more. At the present time, there have been no material changes in the credit quality of these securities resulting in other than temporary impairment, and in Management's opinion, no additional write-down for other-than-temporary impairment is warranted.Information regarding securities temporarily impaired as of December 31, 2013 is summarized below: Less than 12 months 12 months or more Total Fair Unrealized Fair Unrealized Fair UnrealizedAs of December 31, 2013Value Losses Value Losses Value LossesU.S. Government-sponsored agencies$78,724,000 $(12,757,000) $— $— $78,724,000 $(12,757,000)Mortgage-backed securities96,263,000 (4,977,000) 5,451,000 (131,000) 101,714,000 (5,108,000)State and political subdivisions69,406,000 (7,895,000) 7,150,000 (1,548,000) 76,556,000 (9,443,000)Other equity securities— — 50,000 (2,000) 50,000 (2,000) $244,393,000 $(25,629,000) $12,651,000 $(1,681,000) $257,044,000 $(27,310,000)Information regarding securities temporarily impaired as of December 31, 2012 is summarized below: Less than 12 months 12 months or more Total Fair Unrealized Fair Unrealized Fair UnrealizedAs of December 31, 2012Value Losses Value Losses Value LossesU.S. Government-sponsored agencies$15,817,000 $(182,000) $— $— $15,817,000 $(182,000)Mortgage-backed securities9,982,000 (231,000) 2,534,000 (83,000) 12,516,000 (314,000)State and political subdivisions8,621,000 (199,000) — — 8,621,000 (199,000)Other equity securities— — 222,000 (44,000) 222,000 (44,000) $34,420,000 $(612,000) $2,756,000 $(127,000) $37,176,000 $(739,000)The Bank is a member of the Federal Home Loan Bank ("FHLB") of Boston, a cooperatively owned wholesale bank for housing and finance in the six New England States. As a requirement of membership in the FHLB, the Bank must own a minimum required amount of FHLB stock, calculated periodically based primarily on its level of borrowings from the FHLB. The Bank uses the FHLB for much of its wholesale funding needs. As of December 31, 2013 and December 31, 2012, the Bank's investment in FHLB stock totaled $12,875,000 and $13,412,000, respectively. FHLB stock is a restricted equity security and therefore is reported at cost, which equals par value.The Company periodically evaluates its investment in FHLB stock for impairment based on, among other factors, the capital adequacy of the FHLB and its overall financial condition. No impairment losses have been recorded through December 31, 2013. The Bank will continue to monitor its investment in FHLB stock. |

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| - Definition
The entire disclosure for  investments in certain debt and equity securities.
+ References
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