Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2021	Sep. 30, 2020
Deferred income tax assets:
Compensation and benefits	$ 41.7	$ 6.0
Inventory	12.8	10.5
Returns, rebates and incentives	37.5	34.5
Retirement benefits	153.1	306.8
Environmental remediation and other site-related costs	22.8	23.8
Share-based compensation	18.5	18.6
Other accruals and reserves	250.2	68.4
Investments	0.0	31.6
Net operating loss carryforwards	130.4	31.1
Tax credit carryforwards	20.3	17.3
Capital loss carryforwards	15.3	10.8
Other	23.7	16.8
Subtotal	726.3	576.2
Valuation allowance	(32.6)	(58.0)
Net deferred income tax assets	693.7	518.2
Deferred income tax liabilities:
Property	(43.7)	(48.0)
Intangible assets	(160.5)	(25.3)
Investments	(64.3)	0.0
Unremitted earnings of foreign subsidiaries	(42.0)	(28.3)
Other	(2.3)	(1.0)
Deferred income tax liabilities	(312.8)	(102.6)
Total net deferred income tax assets	$ 380.9	$ 415.6