Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance			$ 8,693
Other comprehensive (loss) income, net of tax	$ 117	$ (11)	303	$ 55
Ending balance	10,471		10,471
AOCI Attributable to Parent [Member]
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Ending balance	(935)	(1,049)	(935)	(1,049)
Unrealized Gain (Loss) on Cash Flow Hedges [Member]
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	6	(4)	17	0
Other comprehensive (loss) income, net of tax	(3)	(1)	(14)	(5)
Ending balance	3	(5)	3	(5)
Defined Benefit Plans [Member]
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(21)	(13)	(20)	(13)
Other comprehensive (loss) income, net of tax	0	0	(1)	0
Ending balance	(21)	(13)	(21)	(13)
Foreign Currency Translation Adjustment [Member]
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(1,037)	(1,021)	(1,235)	(1,091)
Other comprehensive (loss) income, net of tax	120	(10)	318	60
Ending balance	$ (917)	$ (1,031)	$ (917)	$ (1,031)