Repurchases of Common Stock (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Equity [Abstract]
Shares repurchased in the open market (in shares)	721	267
Shares acquired through employee surrender for statutory tax withholding (in shares)	30	36
Total shares repurchased (in shares)	751	303
Cost of shares repurchased in the open market	$ 179,623	$ 53,862
Cost of shares for employee surrenders	8,604	7,403
Total cost of shares	$ 188,227	$ 61,265
Average cost per share - open market repurchases (in dollars per share)	$ 249.20	$ 201.41
Average cost per share - employee surrenders (in dollars per share)	288.78	206.35
Average cost per share - total (in dollars per share)	$ 250.77	$ 202.00