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Stock-Based Compensation (Stock Option Activity) (Details) - USD ($)
$ / shares in Units, $ in Thousands
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Number of Shares        
Outstanding, beginning of period (in shares) 350,186 414,769 432,269  
Granted (in shares) 32,750 0 50,000  
Exercised (in shares) (55,666) (62,083) (66,000)  
Canceled/Forfeited (in shares)   (2,500) (1,500)  
Outstanding, end of period (in shares) 327,270 350,186 414,769 432,269
Exercisable (in shares) 278,689      
Weighted Average Grant Date Fair Value        
Outstanding, beginning of period (in dollars per share) $ 19.45 $ 19.07 $ 17.55  
Granted (in dollars per share) 28.15 0.00 22.90  
Exercised (in dollars per share) 20.12 16.79 11.76  
Canceled/Forfeited, weighted average exercise price (in dollars per share)   22.90 30.41  
Outstanding, end of period (in dollars per share) 20.21 $ 19.45 $ 19.07 $ 17.55
Exercisable (in dollars per share) $ 19.12      
Weighted Average Remaining Contractual Life (years)        
Outstanding, weighted average remaining contractual life 4 years 2 months 41 days 4 years 2 months 29 days 5 years 28 days 4 years 8 months 81 days
Exercisable, weighted average remaining contractual life 3 years 5 months 45 days      
Aggregate Intrinsic Value        
Outstanding, aggregate intrinsic value $ 2,255 $ 4,453 $ 1,814 $ 2,786
Exercised, aggregate intrinsic value 446 $ 625 $ 481  
Exercisable, aggregate intrinsic value $ 2,203