Hedging Activities - Schedule of Notional Amounts of Outstanding Derivative Positions (Details) - Derivatives designated for hedge accounting £ in Millions, $ in Millions, $ in Millions	Sep. 30, 2022 CAD ($)	Sep. 30, 2022 GBP (£)	Sep. 30, 2022 USD ($)	Mar. 31, 2022 CAD ($)	Mar. 31, 2022 GBP (£)	Mar. 31, 2022 USD ($)
Fair Value Hedges | Derivatives designated as net investment hedges | GBP
Derivatives, Fair Value [Line Items]
Notional | £		£ 450			£ 450
Derivatives designated as net investment hedges | Net Investment Hedges | CAD
Derivatives, Fair Value [Line Items]
Notional	$ 500			$ 500
Derivatives designated as net investment hedges | Cash Flow Hedges | USD
Derivatives, Fair Value [Line Items]
Notional	$ 1,532			$ 1,678
Floating interest rate swaps | Fair Value Hedges | USD
Derivatives, Fair Value [Line Items]
Notional			$ 750			$ 0
Fixed interest rate swaps | Cash Flow Hedges | USD
Derivatives, Fair Value [Line Items]
Notional			$ 500			$ 500