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| **Uncategorized [Abstract]**                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
| Amortized Cost and Approximate Fair Values of Securities                                                                                        | The amortized cost, gross unrealized gains, gross unrealized losses and approximate fair values of the investment securities at the dates indicated were:  AmortizedCostGross Unrealized GainsGross Unrealized LossesFairValueAvailable for sale at March 31, 2013    U.S. Government-sponsored agency securities$4,228$159 $4,387State and municipal151,3798,615$122159,872U.S. Government-sponsored mortgage-backed securities357,3079,444216366,535Corporate obligations6,173 5,806367Equity securities1,706  1,706Total available for sale520,79318,2186,144532,867Held to maturity at March 31, 2013    State and municipal112,3904,1201116,509U.S. Government-sponsored mortgage-backed securities224,30610,68763234,930Total held to maturity336,69614,80764351,439Total Investment Securities$857,489$33,025$6,208$884,306  AmortizedCostGross Unrealized GainsGross Unrealized LossesFairValueAvailable for sale at December 31, 2012    U.S. Government-sponsored agency securities$4,475$165 $4,640State and municipal148,18710,025$18158,194U.S. Government-sponsored mortgage-backed securities337,63110,99446348,579Corporate obligations6,105 5,881224Equity securities1,706  1,706Total available for sale498,10421,1845,945513,343Held to maturity at December 31, 2012    State and municipal117,2275,4891122,715U.S. Government-sponsored mortgage-backed securities243,79311,68115255,459Total held to maturity361,02017,17016378,174Total Investment Securities$859,124$38,354$5,961$891,517 |
| Amortized Cost and Fair Value of Available for Sale Securities and Held to Maturity Securities by Contractual Maturity                          | The amortized cost and fair value of available for sale securities and held to maturity securities at March 31, 2013, by contractual maturity, are shown below.  Expected maturities will differ from contractual maturities because issuers may have the right to call or prepay obligations with or without call or prepayment penalties.  Available for SaleHeld to Maturity AmortizedCostFairValueAmortizedCostFairValueMaturity Distribution at March 31, 2013:    Due in one year or less$2,811$2,866$1,755$1,759Due after one through five years15,34116,0434,9295,295Due after five through ten years55,10758,08055,40657,228Due after ten years88,52187,63750,30052,227 $161,780$164,626$112,390$116,509U.S. Government-sponsored mortgage-backed securities357,307366,535224,306234,930Equity securities1,7061,706Total Investment Securities$520,793$532,867$336,696$351,439                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
| Gross Gains and Losses on Sales and Redemptions of Available for Sale Securities and Other Than Temporary Impairment Losses Recognized          | Gross gains and losses on the sales and redemptions of available for sale securities, and other-than-temporary impairment (“OTTI”) losses recognized for the three months ended March 31, 2013 and 2012 are shown below. Three Months EndedMarch 31,20132012Sales and Redemptions of Available for Sale Securities:  Gross gains$248$789Gross losses——Other-than-temporary impairment losses——                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
| Investments' Gross Unrealized Losses and Fair Value Aggregated by Investment Category and Length of Time in Continuous Unrealized Loss Position | The following table shows the Corporation’s investments’ gross unrealized losses and fair value, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position at March 31, 2013, and December 31, 2012:  Less than12 Months12 Months or LongerTotal FairValueGrossUnrealizedLossesFairValueGrossUnrealizedLossesFairValueGrossUnrealizedLossesTemporarily Impaired Investment      Securities at March 31, 2013      State and municipal$10,702$123  $10,702$123U.S. Government-sponsored mortgage-backed securities27,183279  27,183279Corporate obligations  $336$5,8063365,806Total Temporarily Impaired Investment Securities$37,885$402$336$5,806$38,221$6,208   Less than12 Months12 Months or LongerTotal FairValueGrossUnrealized LossesFairValueGrossUnrealized LossesFairValueGrossUnrealized LossesTemporarily Impaired Investment      Securities at December 31, 2012      State and municipal$4,524$19  $4,524$19U.S. Government-sponsored mortgage-backed securities12,32061  12,32061Corporate obligations  $194$5,8811945,881Total Temporarily Impaired Investment Securities$16,844$80$194$5,881$17,038$5,961                                                                                                                                                                                                  |
| Investments in Debt and Equity Securities Reported Less than Historical Cost                                                                    | Certain investments in debt and equity securities are reported in the financial statements at an amount less than their historical cost as indicated in the table below.March 31, 2013December 31, 2012Investments reported at less than historical cost:  Historical cost$44,428$22,999Fair value$38,221$17,038Percent of the Corporation's available for sale and held to maturity portfolio4.4%1.9%                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
| Debt Securities Credit Loss Recognized in Income, and Other Losses Recorded in Other Comprehensive Income                                       | The following table provides information about debt securities for which only a credit loss was recognized in income and other losses were recorded in other comprehensive income.  AccumulatedCredit Losses in2013AccumulatedCredit Losses in2012Credit losses on debt securities held:  Balance, January 1$11,355$11,355Additions related to other-than-temporary losses not previously recognizedBalance, March 31$11,355$11,355                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |

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Tabular disclosure of fair value of investments in debt and equity securities in an unrealized loss position categorized neither as held-to-maturity nor trading securities.
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Tabular disclosure of maturities of an entity's investments as well as any other information pertinent to the investments.
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| - Definition
Tabular disclosure of the amount of other than temporary impairment (OTTI) related to credit losses recognized in earnings including: (a) the beginning balance of the amount related to credit losses on debt securities held by the investor at the beginning of the period for which a portion of an OTTI was recognized in other comprehensive income; (b) additions for the amount related to the credit loss for which an OTTI was not previously recognized; (c) reductions for securities sold during the period (realized); (d) reductions for securities for which the amount previously recognized in other comprehensive income was recognized in earnings because the investor intends to sell the security or more likely than not will be required to sell the security before recovery of its amortized cost basis; (e) additional increases to the amount related to the credit loss for which an OTTI was previously recognized when the investor does not intend to sell the security and it is not more likely than not that the investor will be required to sell the security before recovery of its amortized cost basis; (f) reductions for increases in cash flows expected to be collected that are recognized over the remaining life of the security; and (g) the ending balance of the amount related to credit losses on debt securities held by the entity at the end of the period for which a portion of an OTTI was recognized in other comprehensive income.
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Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27340-111563Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name FASB Staff Position (FSP) -Number FAS115-1/124-1 -Paragraph 18B -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.  This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.
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Tabular disclosure of realized gains and losses on investments reported in the statement of income.
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Tabular disclosure of unrealized gains and losses on investments.
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