Discontinued Operations, Goodwill and Intangible Assets - Schedule of Significant Components Included in Statement of Cash Flows for Discontinued Operations (Details) - Held for Sale - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Discontinued Operations, Goodwill and Intangible Assets
Payments for capital expenditures	$ 0.0	$ (2.5)	$ (6.2)
Noncash increase in noncurrent assets held for sale due to deconsolidation of a joint venture	41.6	0.0	0.0
Noncash decrease in noncontrolling interest due to deconsolidation of a joint venture	$ (13.8)	$ 0.0	$ 0.0