Repurchases of Common Stock (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Equity [Abstract]
Shares repurchased in the open market (in shares)	0	86	721	353
Shares acquired through employee surrender for statutory tax withholding (in shares)	0	1	30	37
Total shares repurchased (in shares)	0	87	751	390
Cost of shares repurchased in the open market	$ 0	$ 20,285	$ 179,623	$ 74,147
Cost of shares for employee surrenders	65	169	8,669	7,572
Total cost of shares	$ 65	$ 20,454	$ 188,292	$ 81,719
Average cost per share - open market repurchases (in dollars per share)	$ 0	$ 235.94	$ 249.20	$ 209.81
Average cost per share - employee surrenders (in dollars per share)	312.19	249.77	288.94	207.16
Average cost per share - total (in dollars per share)	$ 312.19	$ 236.04	$ 250.79	$ 209.56