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Hedging Activities - Narrative (Details) £ in Millions, $ in Millions, € in Billions	3 Months Ended	6 Months Ended		12 Months Ended
	Jun. 30, 2023 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Mar. 31, 2023 USD ($)	Jun. 15, 2023 USD ($)	Dec. 31, 2022 GBP (£)	Sep. 30, 2022 EUR (€)
Derivative [Line Items]
Debt outstanding		$ 5,584		$ 5,594
Disposed of by sale | U.K. Disposal Group (Disposal Group)
Derivative [Line Items]
Reclassification of gains from AOCI			$ 26
Fair Value Hedges | USD | Floating interest rate swaps | Derivatives designated for hedge accounting
Derivative [Line Items]
Derivative, notional amount		$ 1,250		1,250
Cash Flow Hedges | Floating interest rate swaps | Derivatives designated for hedge accounting
Derivative [Line Items]
Derivative, notional amount, entered into during period	$ 50			450
Derivative, notional amount					$ 500
Derivative termination proceeds, amortization period (in years)		10 years
Cash Flow Hedges | USD | Fixed interest rate swaps | Derivatives designated for hedge accounting
Derivative [Line Items]
Derivative, notional amount		$ 0		$ 450
Currency swap | Fair Value Hedges | EUR | Derivatives designated for hedge accounting
Derivative [Line Items]
Derivative, notional amount | €							€ 1.1
British Pound Sterling Denominated Notes | Term Loan
Derivative [Line Items]
Debt outstanding | £						£ 450

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