Discontinued Operations - Consolidated Statements of Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended			19 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2024
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income tax expense (benefit)	$ 69.1	$ 37.1	$ 34.7
Income (loss) from discontinued operations, net of tax	(3.0)	1,220.3	314.9
Discontinued Operations, Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net revenues	0.0	1,174.4	2,695.2
Cost of sales	0.0	924.2	2,134.7
Gross profit	0.0	250.2	560.5
Selling, general and administrative expenses	0.0	124.9	304.3
Net legacy and separation-related expenses	14.1	53.7	7.0
Equity and other income, net	0.0	(14.2)	(33.4)
Operating (loss) income from discontinued operations	(14.1)	85.8	282.6
Net pension and other postretirement plan expense (income)	0.0	0.1	(3.4)
Net interest and other financing expenses	0.0	4.4	4.6
Gain on sale of discontinued operations	0.0	(1,571.6)	0.0
(Loss) income before income taxes - discontinued operations	(14.1)	1,652.9	281.4
Income tax expense (benefit)	(11.1)	432.6	(33.5)
Income (loss) from discontinued operations, net of tax	(3.0)	1,220.3	$ 314.9
Currency translation adjustment loss	4.4	30.7
Tax impact on gain on sale of discontinued operations	$ (5.2)	$ 424.3		$ 419.1