Summary of Significant Accounting Policies - Equity Method Investment (Details) $ in Millions		12 Months Ended
	Jul. 01, 2025 USD ($)	Sep. 30, 2025 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)
Schedule of Equity Method Investments [Line Items]
Equity method investments		$ 69.2	$ 9.4
Gain (Loss) on Disposition of Business		(57.2)	0.0	$ 0.0
Disposal Group, Disposed of by Sale, Not Discontinued Operations | TerraSource
Schedule of Equity Method Investments [Line Items]
Proceeds from Divestiture of Interest in Consolidated Subsidiaries	$ 116.7
Gain (Loss) on Disposition of Business	$ 68.1
Disposal Group, Including Discontinued Operation, Ownership Percentage Sold	0.46
TerraSource Holdings, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments		68.8	9.2
Income (Loss) from Equity Method Investments		$ 5.6	$ 5.8	$ 0.1
TerraSource Holdings, LLC | Disposal Group, Disposed of by Sale, Not Discontinued Operations | TerraSource
Schedule of Equity Method Investments [Line Items]
Consideration	$ 245.0