CONSOLIDATED STATEMENTS OF CHANGES IN ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total period activity	$ 239	$ 72	$ (614)
Derivative Instruments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(228)	(203)	(159)
Reclassification adjustments	21	8	(45)
Deferred gain/(loss) on cash flow hedges	(16)	(33)	1
Total period activity	5	(25)	(44)
Ending balance	(223)	(228)	(203)
Translation Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(782)	(878)	(308)
Currency translation adjustments	234	96	(570)
Total period activity	234	96	(570)
Ending balance	(548)	(782)	(878)
Other
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	1	0	0
Other		1
Total period activity		1
Ending balance	1	1	0
Total
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(1,009)	(1,081)	(467)
Reclassification adjustments	21	8	(45)
Deferred gain/(loss) on cash flow hedges	(16)	(33)	1
Currency translation adjustments	234	96	(570)
Other		1
Total period activity	239	72	(614)
Ending balance	$ (770)	$ (1,009)	$ (1,081)