Stockholders' Equity - Accumulated other comprehensive income/ (loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ (726)
Other comprehensive (loss)/gain, net of tax	(4)	$ (97)	$ (124)
Ending balance	(730)	(726)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	3,773	2,708	2,185	$ 1,786
Accumulated Other Comprehensive (Loss)/ Income
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Other comprehensive (loss)/gain, net of tax	(4)	(97)	(124)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(730)	(726)	(629)	(505)
Derivatives Net Unrealized Losses
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Other comprehensive (loss)/gain, net of tax	(15)	4	(1)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(15)	0	(4)	$ (3)
Accumulated Other Comprehensive Income (Loss), Derivative Qualifying as Hedge, Excluded Component, Including Portion Attributable to Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	21	9	0
Other comprehensive (loss)/gain, net of tax	(58)	12	9
Ending balance	(37)	21	9
Currency Translation Adjustment, Net Unrealized Losses
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(724)	(620)	(487)
Other comprehensive (loss)/gain, net of tax	69	(104)	(133)
Ending balance	(655)	(724)	(620)
Benefit Plans, Actuarial Gains/ (Losses)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(23)	(14)	(15)
Other comprehensive (loss)/gain, net of tax	0	(9)	1
Ending balance	$ (23)	$ (23)	$ (14)