Income Taxes - Summary of Valuation Allowance Against Certain Foreign Net Deferred Tax Assets and State Net Operating Losses (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Balance at beginning of year	$ 1,069	$ 651	$ 419
State	235	57	32
U.S.	2,978
Foreign	2,248	478	132
Discontinued operations		(117)	68
Balance at end of year	$ 6,530	$ 1,069	$ 651