Accumulated Other Comprehensive Income/(Loss) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Cumulative Translation Adjustment Summary [Roll Forward]
Beginning Balance	$ (800,000,000)	$ (435,000,000)	$ (890,000,000)	$ (607,000,000)
Net gain/(loss) on Foreign Currency Translation	191,000,000	(141,000,000)	281,000,000	31,000,000
Other Comprehensive Income (Loss), Net of Tax	191,000,000	(141,000,000)	281,000,000	31,000,000
Ending Balance	(609,000,000)	(576,000,000)	(609,000,000)	(576,000,000)
Accumulated Other Comprehensive Income (Loss), Net of Tax	(609,000,000)	(576,000,000)	(609,000,000)	(576,000,000)	$ (890,000,000)
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax [Abstract]
Net gain/(loss) on foreign currency translation, tax adjustment	0	0	0	0
Accumulated Other Comprehensive Income (Loss) [Member]
Cumulative Translation Adjustment Summary [Roll Forward]
Other Comprehensive Income (Loss), Net of Tax	$ 191,000,000	$ (141,000,000)	$ 281,000,000	$ 31,000,000