CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement Of Income And Comprehensive Income [Abstract]
Tax expense (benefit), retirement benefits	$ 9	$ 25	$ 5	$ 21
Tax expense, on long-term investments		2		3
Tax expense, on hedging instruments				6
Tax expense (benefit), cumulative translation adjustment and other	$ 5	$ (2)	$ 6	$ 9