Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cumulative Translation Adjustment Summary [Roll Forward]
Beginning balance	$ (890)	$ (607)	$ 160
Net gain/(loss) on Foreign Currency Transaction	471	(283)	(767)
Ending balance	(419)	(890)	(607)
Total AOCI ending balance at December 31	(419)	(890)	(607)
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax [Abstract]
Net gain/(loss) on foreign currency translation, tax adjustment	0	0	0
Accumulated Other Comprehensive Income (Loss) [Member]
Cumulative Translation Adjustment Summary [Roll Forward]
Other Comprehensive Income/(Loss), Net of Tax	$ 471	$ (283)	$ (767)