Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022
Deferred income tax assets
Compensation and benefits	$ 35.0	$ 26.7
Inventory	15.5	10.4
Returns, rebates, and incentives	75.1	61.7
Retirement benefits	85.4	80.7
Environmental remediation and other site-related costs	23.6	23.6
Share-based compensation	22.7	21.5
Other accruals and reserves	333.3	249.9
Net operating loss carryforwards	60.8	85.2
Tax credit carryforwards	9.2	19.3
Capital loss carryforwards	14.4	13.0
Other	48.1	10.7
Subtotal	723.1	602.7
Valuation allowance	(89.1)	(23.1)
Net deferred income tax assets	634.0	579.6
Deferred income tax liabilities
Property	(44.1)	(36.9)
Intangible assets	(144.8)	(149.8)
Investments	0.0	(26.0)
Unremitted earnings of foreign subsidiaries	(27.2)	(20.0)
Other	(1.8)	(2.1)
Deferred income tax liabilities	(217.9)	(234.8)
Total net deferred income tax assets	$ 416.1	$ 344.8