Accumulated Other Comprehensive Income/(Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	$ (831)	$ (784)	$ (925)	$ (592)
Other comprehensive income/(loss) before reclassifications	(92)	(2)	(81)	(118)
Amounts reclassified from accumulated other comprehensive (income)/loss	(73)	(42)	(87)	(118)
Adjustment to adopt reclassification of certain tax effects from AOCI			97
Other comprehensive income/(loss)	(165)	(44)	(71)	(236)
Balance at end of period	(996)	(828)	(996)	(828)
Foreign currency translation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(758)	(776)	(889)	(587)
Other comprehensive income/(loss) before reclassifications	(160)	(44)	(127)	(233)
Amounts reclassified from accumulated other comprehensive (income)/loss	0	0	0	0
Adjustment to adopt reclassification of certain tax effects from AOCI			98
Other comprehensive income/(loss)	(160)	(44)	(29)	(233)
Balance at end of period	(918)	(820)	(918)	(820)
Derivative financial instruments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(73)	(8)	(36)	(5)
Other comprehensive income/(loss) before reclassifications	68	42	46	115
Amounts reclassified from accumulated other comprehensive (income)/loss	(73)	(42)	(87)	(118)
Adjustment to adopt reclassification of certain tax effects from AOCI			(1)
Other comprehensive income/(loss)	(5)	0	(42)	(3)
Balance at end of period	$ (78)	$ (8)	$ (78)	$ (8)