Income Taxes - Components of Provision for Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current provision:
Federal									$ 299,882	$ 296,400	$ 249,358
State									140,794	132,357	123,264
Deferred expense (benefit):
Federal									5,296	(1,530)	(11,777)
State									1,615	(1,542)	(9,284)
Income tax expense	$ 148,096	$ 162,265	$ 87,869	$ 49,357	$ 94,061	$ 105,075	$ 119,114	$ 107,435	$ 447,587	$ 425,685	$ 351,561