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Stock-Based Compensation (Details) - USD ($)
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Stock options additional disclosures [Abstract]      
Stock-based compensation expense $ 4,378,000 $ 4,086,000 $ 3,521,000
Restricted stock and restricted stock units, weighted average grant date fair value [Abstract]      
Number of shares available for future grant (in shares) 2,994,517    
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) 541,564    
Granted (in shares) 50,508    
Exercised (in shares) (360,147)    
Forfeited (in shares) 0    
Expired (in shares) (1,750)    
Outstanding, end of period (in shares) 230,175 541,564  
Exercisable, end of period (in shares) 163,925    
Expected to vest (in shares) 66,249    
Stock options, weighted average exercise price [Abstract]      
Outstanding, beginning of period (in dollars per share) $ 23.23    
Granted (in dollars per share) 28.95    
Exercised (in dollars per share) 23.32    
Forfeited (in dollars per share) 0    
Expired (in dollars per share) 22.93    
Outstanding, end of period (in dollars per share) 24.35 $ 23.23  
Exercisable, end of period (in dollars per share) 22.70    
Expected to vest (in dollars per share) $ 28.43    
Stock options additional disclosures [Abstract]      
Weighted average remaining contractual term, outstanding, end of period 4 years 5 months 5 days    
Weighted average remaining contractual term, exercisable, end of period 2 years 5 months 19 days    
Weighted average remaining contractual term, expected to vest 9 years 3 months 11 days    
Aggregate intrinsic value, outstanding, end of period $ 4,035,063    
Aggregate intrinsic value, exercisable, end of period 3,144,022    
Aggregate intrinsic value, expected to vest 891,041    
Stock-based compensation expense 200,000 $ 200,000 100,000
Proceeds from stock options exercised 8,398,000 12,044,000 6,554,000
Tax benefits related to stock options exercised 1,223,000 952,000 307,000
Intrinsic value of stock options exercised 3,143,000 2,446,000 789,000
Fair value of shares vested during the year 105,000 $ 63,000 393,000
Restricted Stock [Member]      
Stock options additional disclosures [Abstract]      
Unrecognized compensation cost $ 4,500,000    
Unrecognized compensation cost, weighted average period of recognition 2 years 9 months 18 days    
Restricted stock and restricted stock units [Roll Forward]      
Unvested, beginning of period (in shares) 23,000    
Forfeited (in shares) 0    
Vested (in shares) (23,000)    
Unvested, end of period (in shares) 0 23,000  
Restricted stock and restricted stock units, weighted average grant date fair value [Abstract]      
Unvested, beginning of period (in dollars per share) $ 24.17    
Forfeited (in dollars per share) 0    
Vested (in dollars per share) 24.17    
Unvested, end of period (in dollars per share) $ 0 $ 24.17  
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) 665,008    
Forfeited (in shares) (20,969)    
Vested (in shares) (254,445)    
Granted (in shares) 223,569    
Unvested, end of period (in shares) 613,163 665,008  
Restricted stock and restricted stock units, weighted average grant date fair value [Abstract]      
Unvested, beginning of period (in dollars per share) $ 21.45    
Forfeited (in dollars per share) 20.92    
Vested (in dollars per share) 21.32    
Granted (in dollars per share) 24.47    
Unvested, end of period (in dollars per share) $ 22.62 $ 21.45  
Restricted and Deferred Stock Awards [Member]      
Stock options additional disclosures [Abstract]      
Stock-based compensation expense $ 4,200,000 $ 3,900,000 3,400,000
Tax benefit on restricted stock awards $ 2,900,000 $ 1,500,000 $ 1,100,000