Income Taxes - Summary of Valuation Allowance Against Certain Foreign Net Deferred Tax Assets and State Net Operating Losses (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Balance at beginning of year	$ 651	$ 419	$ 60
State	57	32	7
Foreign	478	132	341
Discontinued operations	(117)	68	11
Balance at end of year	$ 1,069	$ 651	$ 419