Accumulated Other Comprehensive Income/(Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of year	$ (364)	$ 117	$ 176
Other comprehensive income/(loss) before reclassifications	(536)	(485)	(63)
Amounts reclassified from accumulated other comprehensive (income)/loss	3	4	4
Other comprehensive income/(loss)	(533)	(481)	(59)
Balance at end of year	(897)	(364)	117
Foreign currency translation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of year	(359)	122	184
Other comprehensive income/(loss) before reclassifications	(538)	(481)	(62)
Amounts reclassified from accumulated other comprehensive (income)/loss	0	0	0
Other comprehensive income/(loss)	(538)	(481)	(62)
Balance at end of year	(897)	(359)	122
Derivative financial instruments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of year	(5)	(5)	(8)
Other comprehensive income/(loss) before reclassifications	2	(4)	(1)
Amounts reclassified from accumulated other comprehensive (income)/loss	3	4	4
Other comprehensive income/(loss)	5	0	3
Balance at end of year	$ 0	$ (5)	$ (5)