Income Taxes - Components of Income Tax Expense (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Federal
Current	$ 220	$ 234
Deferred	116	19
Federal income tax	336	253
State
Current	30	92
Deferred	12	17
State income tax	42	109
Applicable income taxes	$ 378	$ 362