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Stock Based Compensation (Summary of Stock Option Activity) (Details) - USD ($)
$ / shares in Units, $ in Thousands
 12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Stock Based Compensation [Abstract]    
Options, beginning of year 208,700 212,725
Options, Granted 26,750 28,900
Options, Exercised (32,350) (28,275)
Options, Forfeited (3,275) (4,650)
Options, end of year 199,825 208,700
Options, Exercisable, end of period 173,075 179,800
Weighted Average Exercise Price Per Share, Outstanding, beginning of period $ 22.54 $ 20.76
Weighted Average Exercise Price Per Share, Granted 36.02 32.34
Weighted Average Exercise Price Per Share, Exercised 19.71 18.39
Weighted Average Exercise Price Per Share, Forfeited 24.31 27.08
Weighted Average Exercise Price Per Share, Outstanding, end of period 24.78 22.54
Weighted Average Exercise Price Per Share, Exercisable, end of period $ 23.04 $ 20.97
Aggregate Intrinsic Value, Outstanding, beginning of period $ 2,182,537  
Aggregate Intrinsic Value, Outstanding, end of period 2,822,470 $ 2,182,537
Aggregate Intrinsic Value, Exercisable at end of period $ 2,745,430 $ 2,163,463