Income Taxes - Summary of Gross Unrecognized Income Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Balance at January 1	$ 584	$ 493	$ 479
Increases and decreases as a result of positions taken during prior years
Transfers from valuation allowances	0	0	(3)
Other increases, including currency translation	21	34	37
Other decreases, including currency translation	(24)	(34)	(3)
Balances related to acquired businesses	0	(1)	(3)
Increases as a result of positions taken during the current year	90	109	65
Decreases relating to settlements with tax authorities	(19)	0	(51)
Decreases as a result of a lapse of the applicable statute of limitations	(23)	(17)	(28)
Balance at December 31	$ 629	$ 584	$ 493