Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2024	Sep. 30, 2023
Deferred income tax assets
Compensation and benefits	$ 18.0	$ 35.0
Inventory	22.5	15.5
Returns, rebates, and incentives	62.1	75.1
Retirement benefits	88.4	85.4
Environmental remediation and other site-related costs	23.6	23.6
Share-based compensation	25.5	22.7
Other accruals and reserves	385.5	333.3
Net operating loss carryforwards	69.6	60.8
Tax credit carryforwards	14.2	9.2
Capital loss carryforwards	15.4	14.4
Other	58.5	48.1
Subtotal	783.3	723.1
Valuation allowance	(97.5)	(89.1)
Net deferred income tax assets	685.8	634.0
Deferred income tax liabilities
Property	(52.0)	(44.1)
Intangible assets	(119.8)	(144.8)
Investments	0.0	0.0
Unremitted earnings of foreign subsidiaries	(36.8)	(27.2)
Other	0.0	(1.8)
Deferred income tax liabilities	(208.6)	(217.9)
Total net deferred income tax assets	$ 477.2	$ 416.1