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Stock-Based Compensation - Stock Options and Restricted Stock Narrative (Details) - USD ($)
1 Months Ended 12 Months Ended
Feb. 08, 2018
Sep. 11, 2017
Feb. 28, 2018
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Surrendered stock options (in shares)       168,000 0 8,000
Proceeds from stock options exercised       $ 1,442,000 $ 6,244,000 $ 1,712,000
Tax benefit from stock options exercised       $ 700,000 $ 2,600,000 $ 500,000
Options granted (in shares)       92,000 243,000 77,000
Restricted stock granted (in shares)       133,000 77,000 138,000
Restricted stock vested (in shares)       119,000 146,000 178,000
Minimum            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Vesting period       1 year    
Maximum            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Vesting period       4 years    
Outside directors            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Surrendered stock options (in shares)   150,000        
Stock options            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Modification expense       $ 0 $ 0 $ 0
Unrecognized pre-tax stock-based compensation expense       $ 2,000,000    
Unrecognized pre-tax stock-based compensation expense, period for recognition       1 year 8 months 12 days    
Stock options | Minimum            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Vesting period       3 years    
Stock options | Maximum            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Vesting period       4 years    
Stock options | Outside directors            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Acceleration of stock-based compensation expense       $ 1,200,000    
Non-vested restricted stock award            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Unrecognized pre-tax stock-based compensation expense       $ 7,700,000    
Unrecognized pre-tax stock-based compensation expense, period for recognition       1 year 7 months 6 days    
Non-vested restricted stock award | Minimum            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Vesting period       1 year    
Non-vested restricted stock award | Maximum            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Vesting period       3 years    
Subsequent Event | Certain Executive Employees            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Options granted (in shares) 119,220          
Subsequent Event | Stock options | Certain Executive Employees            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Vesting period 3 years          
Options grant date fair value $ 1,700,000          
Subsequent Event | Stock options | Certain Executive Employees | Percent Vesting on February 8, 2019            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Award vesting rights percentage 33.33%          
Subsequent Event | Stock options | Certain Executive Employees | Quarterly Vesting            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Award vesting rights percentage 8.33%          
Subsequent Event | Non-vested restricted stock award | Certain Executive Employees            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Vesting period     3 years      
Restricted stock granted (in shares)     133,406      
Restricted stock, grant date fair value     $ 6,000,000      
Scenario, Forecast | Non-vested restricted stock award | Certain Executive Employees | Percent Vesting On February 21, 2019            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Award vesting rights percentage     33.33%      
Restricted stock vested (in shares)     95,586      
Scenario, Forecast | Subsequent Event | Non-vested restricted stock award | Certain Executive Employees | Percent Vesting on February 8, 2019            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Award vesting rights percentage     33.33%      
Restricted stock vested (in shares)     37,820      
Scenario, Forecast | Subsequent Event | Non-vested restricted stock award | Certain Executive Employees | Quarterly Vesting            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Award vesting rights percentage     8.33%