Divestitures - Schedule of Discontinued Operations, Income Statement (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income from discontinued operations (net of income tax (benefit) expense)	$ 0.0	$ 2.2	$ 462.6
Gain on divestiture of discontinued operations (net of income tax expense)	0.0	0.0	443.1
Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Revenue	0.0	0.0	213.7
Disposal Group, Including Discontinued Operation, Costs of Goods Sold	0.0	0.0	142.2
Disposal Group, Including Discontinued Operation, Gross Profit (Loss)	0.0	0.0	71.5
Disposal Group, Including Discontinued Operation, Operating Expense	0.0	1.1	42.3
Disposal Group, Including Discontinued Operation, Operating Income (Loss)	0.0	(1.1)	29.2
Discontinued Operation, Tax Effect of Discontinued Operation	0.0	(3.3)	9.7
Income from discontinued operations (net of income tax (benefit) expense)	0.0	2.2	19.5
Discontinued Operation, Tax Effect of Gain (Loss) from Disposal of Discontinued Operation	142.9
Total income from discontinued operations (net of income tax (benefit) expense)	$ 0.0	$ 2.2	$ 462.6