Fair Value Measurements - Accumulated Other Comprehensive Income/Loss (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 3,338	$ 3,297	$ (1,607)
Other comprehensive income/(loss) before reclassifications	(47)	(30)	7
Amounts reclassified from accumulated other comprehensive loss	10
Total other comprehensive income/(loss), net of tax	(37)	(30)	7
Ending balance	2,211	3,338	3,297
Unrealized Net Gains/(Losses) on Derivative Instruments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(13)	0	0
Other comprehensive income/(loss) before reclassifications	(51)	(13)	0
Amounts reclassified from accumulated other comprehensive loss	10
Total other comprehensive income/(loss), net of tax	(41)	(13)	0
Ending balance	(54)	(13)	0
Foreign Currency Translation Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(9)	9	0
Other comprehensive income/(loss) before reclassifications	2	(18)	9
Amounts reclassified from accumulated other comprehensive loss	0
Total other comprehensive income/(loss), net of tax	2	(18)	9
Ending balance	(7)	(9)	9
Other
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(2)	(3)	(1)
Other comprehensive income/(loss) before reclassifications	2	1	(2)
Amounts reclassified from accumulated other comprehensive loss	0
Total other comprehensive income/(loss), net of tax	2	1	(2)
Ending balance	0	(2)	(3)
Total
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(24)	6	(1)
Ending balance	$ (61)	$ (24)	$ 6