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Stock-Based Compensation - Narrative (Details) - USD ($)
$ in Millions
1 Months Ended 12 Months Ended
Apr. 30, 2018
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Unrecognized stock-based compensation expense   $ 11.3    
Weighted average period for recognition of outstanding awards (in years)   2 years    
Shares authorized under stock-based compensation plan (in shares)   3,700,000.0    
Options granted (in Shares)   0 0  
Options forfeited (in Shares)   0 0  
Options expired (in Shares)   0 0  
Options outstanding (in Shares)   0 0  
Options exercised (in Shares)       23,651
Stock Options        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Award vesting period (in years)   3 years    
Award expiration term (in years)   10 years    
Restricted Stock        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Award vesting period (in years)   3 years    
Restricted Stock Units (RSUs)        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Award vesting period (in years)   3 years    
Requisite service period (in years)   10 years    
Performance-based RSUs        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Performance measurement period (in years)   3 years    
Performance-based RSUs | Scenario, Forecast        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Grants in future periods (in Shares) 196,217