Derivative Financial Instruments - Narrative (Details) - USD ($)	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Derivatives, Fair Value [Line Items]
Derivative, notional amount		$ 0
Other comprehensive gain (loss), cash flow hedge, loss, after reclassification and tax	$ 0	(1,000,000)	$ (12,000,000)
Interest Rate Swap
Derivatives, Fair Value [Line Items]
Derivative, notional amount	0	0
Other comprehensive gain (loss), cash flow hedge, loss, after reclassification and tax	0	0
Pre-tax gains (losses) of the company derivative interest rate swaps	0	(1,000,000)
Foreign Exchange Contract | Other Nonoperating Income (Expense)
Derivatives, Fair Value [Line Items]
Realized foreign exchange forward contract gain	1,000,000
Unrealized foreign exchange forward contract gain (loss)	3,000,000
Foreign Exchange Forward
Derivatives, Fair Value [Line Items]
Losses on derivative, net		$ 1,000,000
Short
Derivatives, Fair Value [Line Items]
Derivative, notional amount	460,000,000
Long
Derivatives, Fair Value [Line Items]
Derivative, notional amount	$ 170,000,000