Income Taxes - Components of Provision for Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Current provision:
Federal	$ 435	$ 300	$ 297
State	224	141	132
Deferred expense (benefit):
Federal	3	5	(2)
State	(11)	2	(2)
Income tax expense	$ 651	$ 448	$ 425