Fair Value Measurements - Accumulated Other Comprehensive Income/Loss (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	$ 2,211	$ 3,338
Other comprehensive loss before reclassifications	(73)	(13)
Amounts reclassified from accumulated other comprehensive loss	7
Total other comprehensive loss, net of tax	(66)	(13)
Ending Balance	2,331	3,122
Unrealized Net Gains/(Losses) on Derivative Instruments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(54)	(13)
Other comprehensive loss before reclassifications	(59)	(17)
Amounts reclassified from accumulated other comprehensive loss	7
Total other comprehensive loss, net of tax	(52)	(17)
Ending Balance	(106)	(30)
Foreign Currency Translation Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(7)	(9)
Other comprehensive loss before reclassifications	(14)	2
Amounts reclassified from accumulated other comprehensive loss	0
Total other comprehensive loss, net of tax	(14)	2
Ending Balance	(21)	(7)
Other
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	0	(2)
Other comprehensive loss before reclassifications	0	2
Amounts reclassified from accumulated other comprehensive loss	0
Total other comprehensive loss, net of tax	0	2
Ending Balance	0	0
Total
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(61)	(24)
Ending Balance	$ (127)	$ (37)