Income Taxes - Schedule of Provision for Income Taxes (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Current, Federal	$ 1,129	$ 1,259	$ 916
Current, State	125	119	102
Current, Foreign	37	40	52
Deferred, Federal	75	(163)	3
Deferred, State	(5)	(27)	(5)
Deferred, Foreign	17	33	40
Provision for income taxes	$ 1,378	$ 1,261	$ 1,108