Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement Of Income And Comprehensive Income [Abstract]
Tax benefit on currency translation adjustments	$ (39)	$ (107)	$ (132)
Tax (benefit) expense on pension and other employee benefits	(36)	104	(193)
Tax (benefit) expense on hedging activities	(2)	9	14
Tax expense (benefit) on available-for-sale securities	$ 0	$ 6	$ (2)