Derivative Instruments and Hedging Activities - Narrative (Details) - USD ($)	1 Months Ended	12 Months Ended
	Mar. 31, 2023	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Derivative [Line Items]
Other comprehensive income (loss)		$ 10,000,000	$ (14,000,000)	$ 16,000,000
Pre-tax net losses associated with interest rate hedges		10,000,000
Pre-tax (losses) gains associated with net investment hedges		(42,000,000)	(39,000,000)	$ (57,000,000)
Maximum amount of loss		97,000,000
Cash collateral received		$ 2,000,000	14,000,000
Energy Services
Derivative [Line Items]
Fixed rate (as a percentage)		3.549%
IRPA
Derivative [Line Items]
Derivative, notional amount		$ 0	$ 0
Foreign Exchange Forward
Derivative [Line Items]
Potential exposure coverage, percent (as a percentage)		90.00%
Revolver | Line of Credit
Derivative [Line Items]
Other comprehensive income (loss)	$ 32,000,000