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SSARs (Details) - USD ($)
$ / shares in Units, $ in Millions
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share based compensation arrangement by share based payment award, options and ssars, outstanding, intrinsic value $ 9.0    
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value $ 13.0 $ 35.0 $ 26.0
Weighted average fair value of options and SSARs granted     $ 8.02
Risk-free interest rate     2.10%
Expected stock price volatility     41.00%
Expected Term, Simplified Method     6