| **Share-Based Compensation (Tables)**                                         | 9 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
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| **Disclosure of Compensation Related Costs, Share-based Payments [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| Assumptions Used in the Black Scholes Model                                   | The estimated fair value of the stock options granted during 2013 and in prior year 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 EndedSeptember 30, Nine Months EndedSeptember 30,  20132012 20132012Stock and ESPP Options     Pre-tax compensation expense$89$71 $177$197Income tax expense (benefit)(17)(11) 1(13)Stock and ESPP option expense, net of income taxes$72$60 $178$184Restricted Stock Awards     Pre-tax compensation expense$386$344 $1,108$904Income tax benefit(135)(104) (387)(322)Restricted stock awards expense, net of income taxes$251$240 $721$582Total Share-Based Compensation     Pre-tax compensation expense$475$415 $1,285$1,101Income tax benefit(152)(115) (386)(335)Total share-based compensation expense, net of income taxes$323$300 $899$766 |
| Stock Option Activity Under Stock Option Plans                                | Stock option activity under the Corporation's stock option plans as of September 30, 2013 and changes during the nine months ended September 30, 2013, were as follows: Number ofSharesWeighted-Average Exercise PriceWeighted Average RemainingContractual Term(in Years)AggregateIntrinsicValueOutstanding at January 1, 2013906,636$21.58  Granted22,500$16.50  Exercised(11,250)$7.90  Canceled(104,012)$23.52  Outstanding September 30, 2013813,874$21.463.861,464,190Vested and Expected to Vest at September 30, 2013813,874$21.463.91,464,190Exercisable at September 30, 2013763,074$21.983.521,277,175                                                                                                                                                                                                                                                       |
| Unvested RSAs Outstanding                                                     | The following table summarizes information on unvested RSAs outstanding as of September 30, 2013: Number of SharesWeighted-AverageGrant Date Fair ValueUnvested RSAs at January 1, 2013401,375$9.29Granted118,954$15.47Vested(111,770)$6.15Forfeited(1,700)$11.95Unvested RSAs at September 30, 2013406,859$11.94                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |

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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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| - Definition
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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