Income Taxes - Reconciliation of Liabilities Associated with Uncertain Tax Provisions (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	$ 1,402	$ 1,452	$ 1,453
Additions based on tax positions related to the current year	140	154	146
Additions for tax positions of prior years	136	96	109
Additions related to acquisitions	5	43
Impact of changes in exchange rates	(78)	(62)	(47)
Settlements with tax authorities	(99)	(27)	(64)
Reductions for tax positions of prior years	(203)	(212)	(109)
Reductions due to the lapse of the applicable statute of limitations	(18)	(42)	(36)
Balance at end of year	$ 1,285	$ 1,402	$ 1,452