v3.19.1
Employee Stock-Based Compensation (Details) - USD ($)
$ / shares in Units, shares in Thousands, $ in Millions
3 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Employee stock-based compensation $ 14.8 $ 9.4
2010 Equity Incentive Plan | Restricted stock units    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Restricted stock units granted (in shares) 35 63
Weighted-average grant-date fair value (in usd per share) $ 66.96 $ 61.26
2010 Equity Incentive Plan | Performance based shares    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Weighted-average grant-date fair value (in usd per share) $ 57.51 $ 39.50
Award vesting period (in years) 4 years  
Performance based restricted stock units granted (in shares) 256 444
2010 Equity Incentive Plan | Performance based shares | Chief Executive Officer    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Target share percentage for shares issued 200.00%  
2010 Equity Incentive Plan | Performance based shares | Minimum    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Target share percentage for shares issued 0.00%  
2010 Equity Incentive Plan | Performance based shares | Maximum    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Target share percentage for shares issued 150.00%  
2010 Equity Incentive Plan- Executive Employees | Performance based shares    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Period for recognition (in years) 3 years