Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cumulative Translation Adjustment Summary [Roll Forward]
Beginning balance	$ (419)	$ (890)	$ (607)
Net gain/(loss) on Foreign Currency Transaction	(410)	471	(283)
Ending AOCI balance	$ (829)	$ (419)	$ (890)

Accumulated adjustment, net of tax, that results from the process of translating subsidiary financial statements and foreign equity investments into the reporting currency from the functional currency of the reporting entity, net of reclassification of realized foreign currency translation gains or losses.

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