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Share-Based Compensation - Schedule of Fair Value Options Granted and Assumptions (Details) - USD ($)
$ / shares in Units, $ in Millions
9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Share-based Compensation    
Stock options granted, fair value   $ 0.8
Stock options granted, weighted average fair value (in dollars per share) $ 48.64 $ 48.05
Stock Options    
Share-based Compensation    
Stock options granted, fair value $ 1.0  
Stock options, expiration period (in years) 7 years  
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]    
Dividend yield 0.80% 0.50%
Expected volatility 25.50% 28.00%
Risk-fee interest rate 2.80% 2.10%
Expected life of options (in years) 5 years 8 months 12 days 5 years 8 months 12 days
Forfeiture rate 0.00% 0.00%
Stock Options | Minimum    
Share-based Compensation    
Stock options, vesting period (in years) 3 years  
Stock Options | Maximum    
Share-based Compensation    
Stock options, vesting period (in years) 4 years