Repurchases of Common Stock (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Equity [Abstract]
Shares repurchased in the open market (in shares)	0	330	721	683
Shares acquired through employee surrender for statutory tax withholding (in shares)	1	1	31	38
Total shares repurchased (in shares)	1	331	752	721
Cost of shares repurchased in the open market	$ 0	$ 91,051	$ 179,623	$ 165,198
Cost of shares for employee surrenders	360	277	9,029	7,849
Total cost of shares	$ 360	$ 91,328	$ 188,652	$ 173,047
Average cost per share - open market repurchases (in dollars per share)	$ 0	$ 275.50	$ 249.20	$ 241.56
Average cost per share - employee surrenders (in dollars per share)	393.12	286.65	292.03	209.20
Average cost per share - total (in dollars per share)	$ 393.12	$ 275.53	$ 250.96	$ 239.87