Derivative and Hedging Activities - Narrative (Details)	3 Months Ended	6 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2019 USD ($) counterparty	Mar. 31, 2019 USD ($)
Derivative [Line Items]
Foreign currency cash flow hedge gain to be reclassified during next 12 months	$ 3,000,000	$ 3,000,000
Number of counterparties with concentration of credit risk | counterparty		8
Maximum amount of loss from counterparties with concentration of credit risk		$ 6,000,000
Designated as Hedging Instrument
Derivative [Line Items]
Pretax gain (loss) on derivative instruments	1,000,000	3,000,000
Pretax gain (loss) on derivatives designated for hedge accounting included other comprehensive income	(2,000,000)	(12,000,000)
Designated as Hedging Instrument | Cash Flow Hedging | Foreign currency forward contracts
Derivative [Line Items]
Notational amount of derivative	576,000,000	576,000,000	$ 277,000,000
Designated as Hedging Instrument | Net Investment Hedging | Foreign currency forward contracts
Derivative [Line Items]
Notational amount of derivative	0	0
Designated as Hedging Instrument | Net Investment Hedging | Foreign currency denominated debt
Derivative [Line Items]
Notational amount of derivative	1,900,000,000	1,900,000,000	0
Pretax gain (loss) on derivatives designated for hedge accounting included other comprehensive income	76,000,000	66,000,000
Not Designated as Hedging Instrument | Foreign currency forward contracts
Derivative [Line Items]
Notational amount of derivative	$ 2,500,000,000	$ 2,500,000,000	$ 2,500,000,000