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Stock-based Compensation - Assumptions for TSR Shares (Details) - TSR Performance Share Awards - $ / shares
6 Months Ended
Feb. 19, 2019
Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Granted (in dollars per share) $ 20.63  
Stock price volatility 31.30%  
Risk free rate of return 2.46%  
Minimum expected volatility   24.28%
Maximum expected volatility   29.01%
Minimum risk free interest rate   1.72%
Maximum risk free interest rate   2.08%
Minimum    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Granted (in dollars per share)   $ 11.46
Maximum    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Granted (in dollars per share)   $ 22.04