Income Taxes - Components of Income Tax Expense (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Federal
Current	$ 414	$ 385	$ 1,002	$ 931
Deferred	(59)	(53)	26	(17)
Federal income tax	355	332	1,028	914
State
Current	140	141	280	295
Deferred	(28)	(13)	(14)	54
State income tax	112	128	266	349
Applicable income taxes	$ 467	$ 460	$ 1,294	$ 1,263