Hedging Activities - Schedule of Notional Amounts of Outstanding Derivatives (Details) - Derivatives designated for hedge accounting € in Millions, £ in Millions, $ in Millions, $ in Millions	Sep. 30, 2025 CAD ($)	Sep. 30, 2025 GBP (£)	Sep. 30, 2025 EUR (€)	Sep. 30, 2025 USD ($)	Jun. 30, 2025 USD ($)	Mar. 31, 2025 CAD ($)	Mar. 31, 2025 GBP (£)	Mar. 31, 2025 EUR (€)	Mar. 31, 2025 USD ($)
Cross-currency swaps | Net Investment Hedges | CAD
Derivatives, Fair Value [Line Items]
Notional	$ 6,500					$ 6,500
Cross-currency swaps | Fair Value Hedges | GBP
Derivatives, Fair Value [Line Items]
Notional | £		£ 450					£ 450
Cross-currency swaps | Fair Value Hedges | EUR
Derivatives, Fair Value [Line Items]
Notional | €			€ 1,100					€ 1,100
Floating interest rate swaps | Fair Value Hedges | USD
Derivatives, Fair Value [Line Items]
Notional				$ 750					$ 750
Floating interest rate swaps | Cash Flow Hedges
Derivatives, Fair Value [Line Items]
Notional					$ 1,400
Floating interest rate swaps | Cash Flow Hedges | USD
Derivatives, Fair Value [Line Items]
Notional				$ 0					$ 850
Foreign currency forwards | Cash Flow Hedges | GBP
Derivatives, Fair Value [Line Items]
Notional | £		£ 0					£ 11