Accumulated Other Comprehensive Income (Loss) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Accumulated other comprehensive income (loss) [Line Items]
Accumulated other comprehensive income (loss), balance at beginning of period	$ (303)	$ 68
Other comprehensive income (loss) before reclassifications	(316)	(5)
Accumulated other comprehensive income (loss), balance at end of period	(619)	63
Foreign currency translation adjustment
Accumulated other comprehensive income (loss) [Line Items]
Accumulated other comprehensive income (loss), balance at beginning of period	(304)	67
Other comprehensive income (loss) before reclassifications	(330)	(5)
Accumulated other comprehensive income (loss), balance at end of period	(634)	62
Unrealized gain on available-for-sale securities
Accumulated other comprehensive income (loss) [Line Items]
Accumulated other comprehensive income (loss), balance at beginning of period	1	1
Other comprehensive income (loss) before reclassifications	0	0
Accumulated other comprehensive income (loss), balance at end of period	1	1
Unrealized gain on forward contracts designated as hedges
Accumulated other comprehensive income (loss) [Line Items]
Accumulated other comprehensive income (loss), balance at beginning of period	0	0
Other comprehensive income (loss) before reclassifications	14	0
Accumulated other comprehensive income (loss), balance at end of period	$ 14	$ 0