Accumulated Other Comprehensive Income/(Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	$ (628)	$ 152	$ (364)	$ 117
Other comprehensive income/(loss) before reclassifications	(201)	(317)	(467)	(284)
Amounts reclassified from accumulated other comprehensive (income)/loss	1	1	3	3
Other comprehensive income/(loss)	(200)	(316)	(464)	(281)
Balance at end of period	(828)	(164)	(828)	(164)
Foreign currency translation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(626)	159	(359)	122
Other comprehensive income/(loss) before reclassifications	(200)	(316)	(467)	(279)
Amounts reclassified from accumulated other comprehensive (income)/loss	0	0	0	0
Other comprehensive income/(loss)	(200)	(316)	(467)	(279)
Balance at end of period	(826)	(157)	(826)	(157)
Derivative financial instruments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(2)	(7)	(5)	(5)
Other comprehensive income/(loss) before reclassifications	(1)	(1)	0	(5)
Amounts reclassified from accumulated other comprehensive (income)/loss	1	1	3	3
Other comprehensive income/(loss)	0	0	3	(2)
Balance at end of period	$ (2)	$ (7)	$ (2)	$ (7)