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Stock-Based Compensation - Performance Restricted Stock Units (Details) - PRSUs - USD ($)
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Award vesting (in years) 3 years    
Award vesting, period of average award price 30 days    
Award vesting, period of average award price, first period 30 days    
Award vesting, period of average award price, last period 30 days    
Weighted volatility rate 50.00%    
Fair value of performance units granted $ 2,600,000 $ 2,800,000  
Granted (in shares) 293,083 199,168  
Stock-based compensation expense $ 600,000.0 $ 800,000.0 $ 0
Fair value of awards vested 200,000    
Unamortized stock compensation expense $ 2,200,000    
Compensation cost not yet recognized, period for recognition (in years) 2 years 3 months 14 days    
25th Percentile (Threshold Level)      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Award vesting percentage 50.00%    
50th Percentile (Target Level)      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Award vesting percentage 100.00%    
75th Percentile (Maximum Level)      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Award vesting percentage 150.00%