Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ 8,068
Other comprehensive income (loss) before reclassifications	(18)	$ (240)
Amounts reclassified from accumulated other comprehensive income (loss)	2	(2)
Ending balance	8,554
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(630)	(304)
Other comprehensive income (loss) before reclassifications	(20)	(245)
Amounts reclassified from accumulated other comprehensive income (loss)	0	0
Ending balance	(650)	(549)
Unrealized gain (loss) on forward contracts
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(4)	0
Other comprehensive income (loss) before reclassifications	2	8
Amounts reclassified from accumulated other comprehensive income (loss)	2	(2)
Ending balance	0	6
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	(3)
Amounts reclassified from accumulated other comprehensive income (loss)	0	0
Ending balance	1	(2)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(633)	(303)
Ending balance	$ (649)	$ (545)