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Stock-based Compensation - Stock Options (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]      
Vesting period 4 years    
Expiration period 10 years    
Weighted-average fair value per option granted (in dollars per share) $ 6.52 $ 6.30 $ 8.38
Assumptions:      
Expected term (in years) 6 years 3 months 6 years 3 months 6 years 3 months
Expected volatility 51.60% 38.90% 42.80%
Risk-free interest rate, minimum 1.90% 2.60% 1.90%
Risk-free interest rate, maximum 2.70% 2.90% 2.10%
Dividend yield 0.00% 0.00% 0.00%
Fair value of options vested $ 5.9 $ 11.3 $ 13.0
Intrinsic value of options exercised $ 0.6 $ 25.1 $ 14.2
Stock options      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting period 4 years    
Vesting percentage 25.00%    
Expiration period 10 years