Income Taxes - Reconciliation of Liabilities Associated with Uncertain Tax Provisions (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Balance at beginning of year	$ 1,301	$ 1,433	$ 1,393
Additions based on tax positions related to the current year	76	86	88
Additions for tax positions of prior years	78	65	145
Impact of changes in exchange rates	(3)	2	(41)
Settlements with tax authorities	(15)	(50)	(22)
Reductions for tax positions of prior years	(87)	(176)	(57)
Reductions due to the lapse of the applicable statute of limitations	(79)	(59)	(73)
Balance at end of year	$ 1,271	$ 1,301	$ 1,433