Stockholders' Equity (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended		49 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Feb. 28, 2021	Jun. 30, 2017
Stockholders' Equity
Authorized stock repurchase amount						$ 1,000,000
Cost of shares of common stock repurchased	$ 154,920	$ 237,162	$ 443,439	$ 241,283
Common Stock
Stockholders' Equity
Authorized stock repurchase amount						$ 1,000,000	$ 500,000
Shares of common stock repurchased	2,574	6,975	7,227	7,213	16,933
Cost of shares of common stock repurchased	$ 154,920	$ 237,162	$ 443,439	$ 241,283	$ 795,866