Derivative Instruments (Details)	12 Months Ended
	Mar. 31, 2020 USD ($) counterparty	Mar. 31, 2019 USD ($)
Derivative [Line Items]
Number of counterparties | counterparty	0
Designated as Hedging Instrument
Derivative [Line Items]
Foreign currency cash flow hedge gain to be reclassified into earnings during next 12 months	$ 17,000,000
Pretax gain (loss) on derivatives designated for hedge accounting included other comprehensive income (loss)	(18,000,000)
Pretax gain (loss) on derivative instruments	2,000,000
Not Designated as Hedging Instrument | Foreign currency forward contracts
Derivative [Line Items]
Notional amount of derivative	2,200,000,000	$ 2,500,000,000
Cash Flow Hedges | Designated as Hedging Instrument | Foreign currency forward contracts
Derivative [Line Items]
Notional amount of derivative	455,000,000	277,000,000
Net Investment Hedging | Designated as Hedging Instrument | Foreign currency forward contracts
Derivative [Line Items]
Notional amount of derivative	0	$ 1,700,000,000
Net Investment Hedging | Designated as Hedging Instrument | Foreign currency-denominated debt
Derivative [Line Items]
Notional amount of derivative	1,900,000,000
Pretax gain (loss) on derivatives designated for hedge accounting included other comprehensive income (loss)	$ 53,000,000