Discontinued Operations	12 Months Ended
	Sep. 30, 2021
Discontinued Operations and Disposal Groups [Abstract]
Discontinued Operations	DISCONTINUED OPERATIONSIn fiscal year 2021, income from discontinued operations, net of tax, was $70.3. This included net tax benefits of $60.0 recorded upon release of tax liabilities related to uncertain tax positions for which the statute of limitations expired. Of this benefit, we recorded $51.8 in the fourth quarter for liabilities associated with our former Performance Materials Division ("PMD") and $8.2 in the third quarter for liabilities associated with our former Energy-from-Waste ("EfW") business. Additionally, we recorded a tax benefit of $10.3 in the first quarter of fiscal year 2021 primarily from the settlement of a state tax appeal related to the gain on the sale of PMD in fiscal year 2017. Our consolidated statement of cash flows for the fiscal year ended 30 September 2021 includes $6.7 received as part of the settlement.In fiscal year 2020, loss from discontinued operations, net of tax, was $14.3. This resulted from a pre-tax loss of $19.0 recorded in the second quarter to increase our existing liability for retained environmental obligations associated with the sale of our former Amines business in September 2006. Refer to the Pace discussion within Note 16, Commitments and Contingencies, for additional information. The loss did not have an impact on our cash flows for the fiscal year ended 30 September 2020