Share-Based Compensation - Weighted-Average Assumptions and Resulting Grant Date Fair Value (Details) - Employee Stock Option - $ / shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Schedule of Weighted Average Assumptions for Fair Values of Stock Options[Line Items]
Shares underlying options granted (in shares)	198	117	1,597	1,349
Weighted-average grant date fair value (in dollars per share)	$ 40.62	$ 53.93	$ 42.32	$ 46.95
Weighted-average volatility (as a percent)	33.00%	32.00%	32.00%	35.00%
Weighted-average expected term	4 years 6 months	4 years 6 months	4 years 6 months	4 years 6 months
Range of risk-free rates, minimum (as a percent)	1.50%	2.70%	1.50%	2.20%
Range of risk-free rates, maximum (as a percent)	1.70%	2.80%	2.50%	2.80%
Expected dividend yield (as a percent)	0.00%	0.00%	0.00%	0.00%