Derivative Instruments - Narrative (Details) $ in Millions	12 Months Ended
	Mar. 31, 2021 USD ($) counterparty	Mar. 31, 2020 USD ($)
Derivative [Line Items]
Number of counterparties | counterparty	5
Designated as Hedging Instrument
Derivative [Line Items]
Foreign currency cash flow hedge gain to be reclassified into earnings during next 12 months	$ 3
Pretax gain (loss) on derivatives designated for hedge accounting included other comprehensive income (loss)	19
Pretax gain (loss) on derivative instruments	(5)
Not Designated as Hedging Instrument | Foreign currency forward contracts
Derivative [Line Items]
Notional amount of derivative	2,100	$ 2,200
Cash Flow Hedges | Designated as Hedging Instrument | Foreign currency forward contracts
Derivative [Line Items]
Notional amount of derivative	546	455
Net Investment Hedging | Designated as Hedging Instrument | Foreign currency-denominated debt
Derivative [Line Items]
Notional amount of derivative	800	$ 1,900
Pretax gain (loss) on derivatives designated for hedge accounting included other comprehensive income (loss)	$ (93)