Accumulated Other Comprehensive Income/(Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	$ (925)	$ (592)
Other comprehensive income/(loss) before reclassifications	10	39
Amounts reclassified from accumulated other comprehensive (income)/loss	(11)	20
Adjustment to adopt reclassification of certain tax effects from AOCI	97
Other comprehensive income/(loss)	96	59
Balance at end of period	(829)	(533)
Foreign currency translation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(889)	(587)
Other comprehensive income/(loss) before reclassifications	13	65
Amounts reclassified from accumulated other comprehensive (income)/loss	0	0
Adjustment to adopt reclassification of certain tax effects from AOCI	98
Other comprehensive income/(loss)	111	65
Balance at end of period	(778)	(522)
Derivative financial instruments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(36)	(5)
Other comprehensive income/(loss) before reclassifications	(3)	(26)
Amounts reclassified from accumulated other comprehensive (income)/loss	(11)	20
Adjustment to adopt reclassification of certain tax effects from AOCI	(1)
Other comprehensive income/(loss)	(15)	(6)
Balance at end of period	$ (51)	$ (11)