Intangible Assets, Goodwill, Acquisitions, and Divestitures - Schedule of Intangible Assets (Details) - USD ($) $ in Millions	Mar. 31, 2025	Sep. 30, 2024
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 715.9	$ 715.9
Accumulated Amortization	(635.3)	(620.1)
Customer Relationships
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	715.9	715.9
Accumulated Amortization	$ (635.3)	$ (620.1)
Customer Relationships | Minimum
Finite Lived Intangible Assets [Line Items]
Estimated Useful Life	6 years
Customer Relationships | Maximum
Finite Lived Intangible Assets [Line Items]
Estimated Useful Life	21 years