Derivative Financial Instruments - Narrative (Details) - USD ($)	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Derivatives, Fair Value [Line Items]
Derivative, notional amount	$ 0	$ 0
Deferred gains (losses) in comprehensive loss related to foreign exchange hedging	0	0
Other comprehensive gain (loss), cash flow hedge, loss, after reclassification and tax	(1,000,000)	(12,000,000)	$ 30,000,000
Interest Rate Swap
Derivatives, Fair Value [Line Items]
Derivative, notional amount	0	500,000,000
Other comprehensive gain (loss), cash flow hedge, loss, after reclassification and tax	0	1,000,000
Pre-tax gains (losses) of the company derivative interest rate swaps	(1,000,000)	(16,000,000)
Foreign Exchange Forward
Derivatives, Fair Value [Line Items]
Losses on derivative, net	$ 1,000,000	$ 6,000,000