Leases - Cash Flow Supplemental Disclosure (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Supplemental Cash Flow Information [Abstract]
Operating cash flows from operating leases included in the measurement of operating lease liabilities	$ 45.1	$ 109.6	$ 125.6
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	$ 31.2	$ 448.9	$ 45.4