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Stock-Based Compensation (Details) - USD ($)
$ / shares in Units, $ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Additional disclosures [Abstract]      
Stock-based compensation expense $ 3,644 $ 4,378 $ 4,086
Restricted stock and restricted stock units, weighted average grant date fair value [Abstract]      
Number of shares available for future grant (in shares) 2,813,597    
Stock Options [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Stock awards vesting period 4 years    
Stock awards termination period 10 years    
Stock options [Roll Forward]      
Outstanding, beginning of period (in shares) 230,174    
Granted (in shares) 1,500    
Exercised (in shares) (118,844)    
Expired (in shares) (800)    
Outstanding, end of period (in shares) 112,030 230,174  
Exercisable, end of period (in shares) 107,280    
Expected to vest (in shares) 4,750    
Stock options, weighted average exercise price [Abstract]      
Outstanding, beginning of period (in dollars per share) $ 24.35    
Granted (in dollars per share) 40.63    
Exercised (in dollars per share) 25.94    
Expired (in dollars per share) 24.46    
Outstanding, end of period (in dollars per share) 22.88 $ 24.35  
Exercisable, end of period (in dollars per share) 22.41    
Expected to vest (in dollars per share) $ 33.52    
Additional disclosures [Abstract]      
Weighted average remaining contractual term, outstanding, end of period 2 years 1 month 17 days    
Weighted average remaining contractual term, exercisable, end of period 1 year 10 months 2 days    
Weighted average remaining contractual term, expected to vest 8 years 8 months 5 days    
Aggregate intrinsic value, outstanding, end of period $ 15,656    
Aggregate intrinsic value, exercisable, end of period 1,544    
Aggregate intrinsic value, expected to vest 22    
Stock-based compensation expense 100 $ 200 200
Proceeds from stock options exercised 3,083 8,398 12,044
Tax benefits related to stock options exercised 650 1,223 952
Intrinsic value of stock options exercised 1,699 3,143 2,446
Fair value of shares vested during the year 329 105 63
Restricted Stock [Member]      
Additional disclosures [Abstract]      
Stock-based compensation expense $ 3,500 $ 4,200 3,900
Restricted Stock [Member] | Employees [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Stock awards vesting period 5 years    
Restricted Stock [Member] | Non-employee Directors [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Stock awards vesting period 3 years    
Restricted Stock Units (RSUs) [Member]      
Restricted stock and restricted stock units [Roll Forward]      
Unvested, beginning of period (in shares) 613,163    
Forfeited (in shares) (5,545)    
Vested (in shares) (198,652)    
Granted (in shares) 125,772    
Unvested, end of period (in shares) 534,738 613,163  
Restricted stock and restricted stock units, weighted average grant date fair value [Abstract]      
Unvested, beginning of period (in dollars per share) $ 22.62    
Forfeited (in dollars per share) 23.18    
Vested (in dollars per share) 22.34    
Granted (in dollars per share) 36.15    
Unvested, end of period (in dollars per share) $ 25.77 $ 22.62  
Restricted Stock Awards and Stock Units [Member]      
Additional disclosures [Abstract]      
Tax benefit on restricted stock awards $ 2,500 $ 2,900 $ 1,500
Unrecognized compensation cost $ 4,800    
Unrecognized compensation cost, weighted average period of recognition 2 years 1 month 6 days