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Equity Incentive Plans and Stock-Based Compensation - Information About Stock Options (Details) - shares
1 Months Ended 3 Months Ended 12 Months Ended
Oct. 31, 2018
Oct. 31, 2016
Feb. 29, 2016
Mar. 31, 2019
Dec. 31, 2015
Dec. 31, 2014
MSUs            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Granted (in shares)         40,000 540,000
Number of consecutive trading days       20 days    
Measurement period       4 years    
PSUs, February 2016            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Granted (in shares)     547,000      
Actual performance vesting percentage     80.00%      
Vested in period (in shares)       253,203    
Forfeited in period (in shares)       200,297    
PSUs, October 2016            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Granted (in shares)   60,641        
Vested in period (in shares)       30,320    
Forfeited in period (in shares)       30,321    
PSUs, October 2018            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Granted (in shares) 464,888          
Vested in period (in shares)       0    
Tranche One | PSUs, February 2016            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Award vesting percentage       80.00%    
Tranche One | PSUs, October 2018            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Award vesting percentage 75.00%          
Tranche Two | PSUs, October 2018            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Award vesting percentage 25.00%