Income Taxes (Components of Income Tax Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Federal, current	$ 669	$ 570	$ 739
State, current	158	152	178
Total current	827	722	917
Federal, deferred	(373)	187	13
State, deferred	(28)	(8)	(2)
Total deferred	(401)	179	11
Total	$ 426	$ 901	$ 928