Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2025	Sep. 30, 2024
Deferred income tax assets
Compensation and benefits	$ 31.0	$ 18.0
Inventory	24.0	23.0
Returns, rebates, and incentives	61.0	62.0
Retirement benefits	45.0	88.0
Environmental remediation and other site-related costs	25.0	24.0
Share-based compensation	23.0	26.0
Other accruals and reserves	470.0	386.0
Net operating loss carryforwards	62.0	70.0
Tax credit carryforwards	13.0	14.0
Capital loss carryforwards	16.0	15.0
Other	125.0	58.0
Subtotal	895.0	784.0
Valuation allowance	(129.0)	(98.0)
Net deferred income tax assets	766.0	686.0
Deferred income tax liabilities
Property	(60.0)	(52.0)
Intangible assets	(105.0)	(120.0)
Investments	0.0	0.0
Unremitted earnings of foreign subsidiaries	(45.0)	(37.0)
Other	0.0	0.0
Deferred income tax liabilities	(210.0)	(209.0)
Total net deferred income tax assets	$ 556.0	$ 477.0