Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance			$ 8,693
Other comprehensive (loss) income, net of tax	$ 96	$ (86)	186	$ 66
Ending balance	9,156		9,156
AOCI Attributable to Parent [Member]
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Ending balance	(1,052)	(1,038)	(1,052)	(1,038)
Unrealized Gain (Loss) on Cash Flow Hedges [Member]
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	13	0	17	0
Other comprehensive (loss) income, net of tax	(7)	(4)	(11)	(4)
Ending balance	6	(4)	6	(4)
Defined Benefit Plans [Member]
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(20)	(14)	(20)	(13)
Other comprehensive (loss) income, net of tax	(1)	1	(1)	0
Ending balance	(21)	(13)	(21)	(13)
Foreign Currency Translation Adjustment [Member]
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(1,141)	(938)	(1,235)	(1,091)
Other comprehensive (loss) income, net of tax	104	(83)	198	70
Ending balance	$ (1,037)	$ (1,021)	$ (1,037)	$ (1,021)