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Stock-Based Compensation - Assumptions for Share Based Awards (Details) - TSR Performance Share Awards - $ / shares
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Liability      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Stock price volatility, minimum rate 29.90% 29.10% 40.40%
Stock price volatility, maximum rate 31.10% 36.70% 43.00%
Risk free rate of return, minimum rate 2.50% 1.80% 0.90%
Risk free rate of return, maximum rate 2.60% 1.90% 1.20%
Stockholders' Equity      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Fair value per performance share award granted during the period $ 19.92 $ 19.85 $ 18.57
Stock price volatility 37.30% 37.80% 34.40%
Risk free rate of return 2.40% 1.40% 0.90%
Minimum | Liability      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Fair value per performance share award granted during the period $ 15.15 $ 13.23 $ 5.59
Maximum | Liability      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Fair value per performance share award granted during the period $ 20.12 $ 21.64 $ 7.10