Condensed Consolidated Statements of Comprehensive Income (Unaudited) (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement Of Income And Comprehensive Income [Abstract]
Tax (benefit) expense on currency translation adjustments	$ 21	$ (2)	$ 69	$ (12)
Tax expense on pension and other employee benefits	6	11	26	32
Tax benefit on hedging activities	(2)	0	(7)	(5)
Tax expense on available-for-sale securities	$ 0	$ 0	$ 1	$ 0