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Hedging Activities - Narrative (Details) € in Millions, £ in Millions, $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2025 CAD ($)	Jun. 30, 2023 USD ($)	Mar. 31, 2025 USD ($)	Mar. 31, 2024 USD ($)	Mar. 31, 2023 USD ($)	Apr. 30, 2025 USD ($)	Mar. 31, 2025 EUR (€)	Mar. 31, 2025 GBP (£)	Mar. 31, 2025 CAD ($)	Dec. 31, 2024 GBP (£)	Dec. 31, 2024 CAD ($)	Jun. 30, 2024 CAD ($)	Mar. 31, 2024 EUR (€)	Mar. 31, 2024 GBP (£)	Mar. 31, 2024 CAD ($)	Jun. 15, 2023 USD ($)	Mar. 31, 2023 EUR (€)	Feb. 28, 2023 GBP (£)	Dec. 31, 2022 GBP (£)	Sep. 30, 2022 EUR (€)	Mar. 31, 2022 EUR (€)
Derivative [Line Items]
Total debt			$ 5,654,000,000	$ 5,629,000,000
Other comprehensive income (loss), cash flow hedge, gain (loss), reclassification before tax			0	0	$ 0
Gain on derivative termination					97,000,000
Fair Value Hedges | Derivatives designated for hedge accounting: | Interest Rate Swap
Derivative [Line Items]
Notional amounts of derivative			1,300,000,000
Derivative, notional mount, terminated			500,000,000
Cash Flow Hedging | Derivatives designated for hedge accounting: | Currency Swap
Derivative [Line Items]
Other comprehensive income (loss), cash flow hedge, gain (loss), reclassification before tax			(4,000,000)	39,000,000	(54,000,000)
Cash Flow Hedging | Derivatives designated for hedge accounting: | Interest rate swap locks, Foreign currency forwards and Other
Derivative [Line Items]
Other comprehensive income (loss), cash flow hedge, gain (loss), reclassification before tax			(6,000,000)	0	0
Cash Flow Hedging | Derivatives designated for hedge accounting: | Interest Rate Swap
Derivative [Line Items]
Notional amounts of derivative			$ 850,000,000													$ 500,000,000
Derivative, notional mount, terminated					500,000,000
Derivative, notional amount, entered into during period		$ 50,000,000			450,000,000
Derivative, termination proceeds, amortization period			10 years
Gain on derivative termination					97,000,000
Cash Flow Hedging | Derivatives designated for hedge accounting: | Interest Rate Swap | Subsequent Event
Derivative [Line Items]
Notional amounts of derivative						$ 550,000,000
British Pound Sterling Denominated Notes | Loans payable
Derivative [Line Items]
Total debt | £																			£ 450
EUR | Fair Value Hedges | Derivatives designated for hedge accounting: | Currency Swap
Derivative [Line Items]
Notional amounts of derivative | €							€ 1,100						€ 1,100
EUR | Currency Swap | Net Investment Hedging | Derivatives designated for hedge accounting:
Derivative [Line Items]
Notional amounts of derivative | €																	€ 1,100			€ 1,100	€ 1,100
EUR | Currency Swap | Fair Value Hedges | Derivatives designated for hedge accounting:
Derivative [Line Items]
Notional amounts of derivative																	€ 1,100	£ 450
USD | Fair Value Hedges | Derivatives designated for hedge accounting: | Interest Rate Swap Entered Into YTD
Derivative [Line Items]
Notional amounts of derivative					1,300,000,000
USD | Fair Value Hedges | Derivatives designated for hedge accounting: | Interest Rate Swap
Derivative [Line Items]
Notional amounts of derivative			$ 750,000,000	1,250,000,000
USD | Cash Flow Hedging | Derivatives designated for hedge accounting: | Interest Rate Swap
Derivative [Line Items]
Notional amounts of derivative			$ 850,000,000	$ 0
GBP | Fair Value Hedges | Derivatives designated for hedge accounting: | Currency Swap
Derivative [Line Items]
Notional amounts of derivative | £								£ 450						£ 450
GBP | Cash Flow Hedging | Derivatives designated for hedge accounting: | Interest rate swap locks, Foreign currency forwards and Other
Derivative [Line Items]
Notional amounts of derivative | £								£ 11		£ 45				£ 39
CAD | Net Investment Hedging | Derivatives designated for hedge accounting: | Currency Swap
Derivative [Line Items]
Notional amounts of derivative									$ 6,500		$ 6,000	$ 2,500			$ 1,500
Derivative, notional mount, terminated											$ 5,000	$ 1,500
Derivative, notional amount, entered into during period	$ 3,000
Disposed of by Sale | European Businesses (Disposal Group)
Derivative [Line Items]
Reclassification from AOCI, current period, before tax					112,000,000
Disposed of by Sale | U.K. Businesses (Disposal Group)
Derivative [Line Items]
Reclassification from AOCI, current period, before tax, attributable to parent					$ 26,000,000

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