| **Share-Based Compensation (Tables)**          | 3 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
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| **Uncategorized [Abstract]**                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| Assumptions Used in the Black Scholes Model    | The estimated fair value of the stock options granted during 2013 and in prior years was calculated using a Black Scholes option pricing model.  The following summarizes the assumptions used in the 2013 Black Scholes model:Risk-free interest rate1.25%Expected price volatility45.68%Dividend yield2.96%Forfeiture rate4.73%Weighted-average expected life, until exercise7.3 years                                                                                                                                                                                                                                                             |
| Components of Share Based Compensation Awards  | The following table summarizes the components of the Corporation's share-based compensation awards recorded as expense:Three Months EndedMarch 31, 20132012Stock and ESPP Options  Pre-tax compensation expense$38$46Income tax benefit(2)Stock and ESPP option expense, net of income taxes$36$46Restricted Stock Awards  Pre-tax compensation expense$336$280Income tax benefit(117)(106)Restricted stock awards expense, net of income taxes$219$174Total Share-Based Compensation:  Pre-tax compensation expense$374$326Income tax benefit(119)(106)Total share-based compensation expense, net of income taxes$255$220 |
| Stock Option Activity Under Stock Option Plans | Stock option activity under the Corporation's stock option plans as of March 31, 2013 and changes during the three months ended March 31, 2013, were as follows: Number ofSharesWeighted-Average Exercise PriceWeighted Average RemainingContractual Term(in Years)AggregateIntrinsicValueOutstanding at January 1, 2013906,636$21.58  Granted9,000$15.32  Exercised(2,250)$6.99  Canceled(8,471)$24.69  Outstanding March 31, 2013904,915$21.603.871,140,887Vested and Expected to Vest at March 31, 2013904,915$21.603.871,140,887Exercisable at March 31, 2013867,615$22.003.641,023,790             |
| Unvested RSAs Outstanding                      | The following table summarizes information on unvested RSAs outstanding as of March 31, 2013: Number of SharesWeighted-AverageGrant Date Fair ValueUnvested RSAs at January 1, 2013401,375$9.29Granted109,118$14.74Vested(100,123)$5.95Forfeited(200)$11.38Unvested RSAs at March 31, 2013410,170$11.55                                                                                                                                                                                                                                                                                                                                              |

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| - Definition
Tabular disclosure of the allocation of equity-based compensation costs to a given line item on the balance sheet and income statement for the period. This may include the reporting line for the costs and the amount capitalized and expensed.
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| - Definition
Tabular disclosure of the changes in outstanding nonvested restricted stock units.
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Tabular disclosure of the number and weighted-average exercise prices (or conversion ratios) for share options (or share units) that were outstanding at the beginning and end of the year, vested and expected to vest, exercisable or convertible at the end of the year, and the number of share options or share units that were granted, exercised or converted, forfeited, and expired during the year.
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| - Definition
Tabular disclosure of the significant assumptions used during the year to estimate the fair value of stock options, including, but not limited to: (a) expected term of share options and similar instruments, (b) expected volatility of the entity's shares, (c) expected dividends, (d) risk-free rate(s), and (e) discount for post-vesting restrictions.
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