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Stock-Based Compensation - Schedule of Assumptions Used to Calculate Fair Value of Stock Options (Details) - Stock Options - $ / shares
6 Months Ended 12 Months Ended
Jun. 30, 2019
Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Weighted average fair value (in dollars per share) $ 58.28 $ 51.27
Weighted average expected life (in years) 6 years 6 years
Weighted average exercise price (in dollars per share) $ 184.81 $ 158.23
Expected stock price volatility (as a percent) 27.21% 27.35%
Weighted average risk–free rate 2.37% 2.69%