Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ 8,068	$ 7,233
Ending balance	9,119	8,068
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(633)	(303)
Other comprehensive income (loss) before reclassifications	8	(315)
Amounts reclassified from accumulated other comprehensive income (loss) into earnings	(4)	(15)
Ending balance	(629)	(633)
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(630)	(304)
Other comprehensive income (loss) before reclassifications	(29)	(326)
Amounts reclassified from accumulated other comprehensive income (loss) into earnings	0	0
Ending balance	(659)	(630)
Unrealized gain (loss) on available-for- sale securities
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	1	1
Other comprehensive income (loss) before reclassifications	0	1
Amounts reclassified from accumulated other comprehensive income (loss) into earnings	0	(1)
Ending balance	1	1
Unrealized gain (loss) on forward contracts
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(4)	0
Other comprehensive income (loss) before reclassifications	37	10
Amounts reclassified from accumulated other comprehensive income (loss) into earnings	(4)	(14)
Ending balance	$ 29	$ (4)