Discontinued Operations - Consolidated Statements of Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income tax expense (benefit)	$ 37.1	$ 34.7	$ 59.9
(Loss) income from discontinued operations, net of tax	1,220.3	314.9	220.2
Discontinued Operations, Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net revenues	1,174.4	2,695.2	2,086.7
Cost of sales	924.2	2,134.7	1,540.9
Gross profit	250.2	560.5	545.8
Selling, general and administrative expenses	124.9	304.3	294.7
Net legacy and separation-related expenses	53.7	7.0	0.0
Equity and other income, net	(14.2)	(33.4)	(36.3)
Operating income from discontinued operations	85.8	282.6	287.4
Net pension and other postretirement plan expense (income)	0.1	(3.4)	1.9
Net interest and other financing expenses	4.4	4.6	2.5
Gain on sale of discontinued operations	(1,571.6)	0.0	0.0
Income before income taxes - discontinued operations	1,652.9	281.4	283.0
Income tax expense (benefit)	432.6	(33.5)	62.8
(Loss) income from discontinued operations, net of tax	1,220.3	$ 314.9	$ 220.2
Currency translation adjustment loss	30.7
Tax impact on gain on sale of discontinued operations	424.3
Tax impact on gain on sale of discontinued operations, current	335.6
Tax impact on gain on sale of discontinued operations, deferred	$ 88.7