Accumulated Other Comprehensive Loss - Narrative (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Mar. 31, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Estimate of gains related to foreign currency exchange contracts during the next 12 months		$ 4		$ 4
Payment from settlement of cash flow hedges, recorded in AOCL, net of tax	$ 183	6	$ (4)	1	$ (134)
Estimated interest expense related to settled interest rate hedge contracts during the next twelve months		21		21
Foreign currency translation adjustment		(92)	$ 28	(38)	$ 28
Foreign currency forward exchange contracts | Indian Rupee
Accumulated Other Comprehensive Income (Loss) [Line Items]
Notional amount of derivatives		206		206		$ 178
Total fair value of cash flow hedge derivatives		$ 5		$ 5		$ 4
Treasury Lock
Accumulated Other Comprehensive Income (Loss) [Line Items]
Derivative liability, notional amount							$ 5,000