Accumulated Other Comprehensive Loss - Narrative (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Mar. 31, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Estimate of losses related to foreign currency exchange contracts during the next 12 months		$ 2		$ 2
Fair market value adjustment on cash flow hedges, net of income tax benefit (provision) of ($1 million), $36 million, $2 million and $45 million	$ 183	3	$ (107)	(5)	$ (130)
Estimated interest expense related to settled interest rate hedge contracts during the next twelve months		21		21
Foreign currency translation adjustment		(1)		54
Foreign currency forward exchange contracts | Indian Rupee
Accumulated Other Comprehensive Income (Loss) [Line Items]
Notional amount of derivatives		256		256		$ 178
Total fair value of cash flow hedge derivatives		$ 2		$ 2		$ 4
Treasury Lock
Accumulated Other Comprehensive Income (Loss) [Line Items]
Derivative liability, notional amount							$ 5,000