|**Share-Based Compensation (Tables)**                       | 6 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
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|**Share-based Payment Arrangement [Abstract]**              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       
|Schedule of components of share-based compensation awards   | The following table summarizes the components of the Corporation's share-based compensation awards recorded as an expense and the income tax benefit of such awards.Three Months EndedJune 30,Six Months EndedJune 30,2020201920202019Stock and ESPP OptionsPre-tax compensation expense$12$25$53$36Income tax benefit(29)(41)(29)(57)Stock and ESPP option expense, net of income taxes$(17)$(16)$24$(21)Restricted Stock AwardsPre-tax compensation expense$1,202$819$2,380$1,789Income tax benefit(236)(186)(493)(726)Restricted stock awards expense, net of income taxes$966$633$1,887$1,063Total Share-Based CompensationPre-tax compensation expense$1,214$844$2,433$1,825Income tax benefit(265)(227)(522)(783)Total share-based compensation expense, net of income taxes$949$617$1,911$1,042
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|                                                            | Three Months EndedJune 30,                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
|                                                            | 2020                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|Stock and ESPP Options                                      |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       
|Pre-tax compensation expense                                | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Income tax benefit                                          | (29                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
|Stock and ESPP option expense, net of income taxes          | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Restricted Stock Awards                                     |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       
|Pre-tax compensation expense                                | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Income tax benefit                                          | (236                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|Restricted stock awards expense, net of income taxes        | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Total Share-Based Compensation                              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       
|Pre-tax compensation expense                                | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Income tax benefit                                          | (265                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|Total share-based compensation expense, net of income taxes | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Schedule of stock option activity under stock option plans  | Stock option activity under the Corporation's stock option plans as ofJune 30, 2020and changes during thesix months ended June 30, 2020, were as follows:Number ofSharesWeighted-Average Exercise PriceWeighted Average RemainingContractual Term(in Years)AggregateIntrinsicValueOutstanding at January 1,202059,350$13.51Exercised(10,050)$8.29OutstandingJune 30, 202049,300$14.572.32$640,876Vested and Expected to Vest at June 30,202049,300$14.572.32$640,876Exercisable at June 30, 202049,300$14.572.32$640,876                                                                                                                                                                                                                                                                              
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|                                                            | Number ofShares                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       
|Outstanding at January 1,2020                               | 59,350                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                
|Exercised                                                   | (10,050                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               
|OutstandingJune 30, 2020                                    | 49,300                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                
|Vested and Expected to Vest at June 30,2020                 | 49,300                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                
|Exercisable at June 30, 2020                                | 49,300                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                
|Schedule of Unvested RSAs outstanding                       | The following table summarizes information on unvested RSAs outstanding as ofJune 30, 2020:Number of SharesWeighted-AverageGrant Date Fair ValueUnvested RSAs at January 1,2020351,048$40.67Granted14,657$27.00Vested(8,591)$40.09Forfeited(525)$40.44Unvested RSAs atJune 30, 2020356,589$40.62                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
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|                                                            | Number of Shares                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
|Unvested RSAs at January 1,2020                             | 351,048                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               
|Granted                                                     | 14,657                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                
|Vested                                                      | (8,591                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                
|Forfeited                                                   | (525                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|Unvested RSAs atJune 30, 2020                               | 356,589                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               

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