Derivative Instruments - Narrative (Details) - USD ($)	3 Months Ended		6 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Mar. 31, 2019
Derivative [Line Items]
Cash flow hedge adjustments, net of tax	$ (3,000,000)	$ 6,000,000	$ (21,000,000)	$ 5,000,000
Interest Rate Swap
Derivative [Line Items]
Pre-tax impact of gain (loss) on derivatives	(4,000,000)	8,000,000	(28,000,000)	$ 7,000,000
Cash flow hedge adjustments, net of tax	(3,000,000)		(21,000,000)
Interest Rate Swap | Interest Expense
Derivative [Line Items]
Gain on cash flow hedge ineffectiveness		$ (5,000,000)
Derivatives Designated for Hedge Accounting | Interest Rate Swap
Derivative [Line Items]
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months	2,000,000		3,000,000
Foreign currency cash flow hedge gain to be reclassified during next 12 months	18,000,000		18,000,000
Derivative liability, fair value	55,000,000		55,000,000		$ 26,000,000
Derivatives Designated for Hedge Accounting | Interest Rate Swap | Other Current Liabilities
Derivative [Line Items]
Derivative liability, fair value	16,000,000		16,000,000		4,000,000
Derivatives Designated for Hedge Accounting | Interest Rate Swap | Other Liabilities
Derivative [Line Items]
Derivative liability, fair value	39,000,000		39,000,000		$ 22,000,000
Derivatives Designated for Hedge Accounting | Cash Flow Hedging | Interest Rate Swap
Derivative [Line Items]
Derivative notional amount	$ 1,600,000,000		$ 1,600,000,000