Leases - Components of Lease Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Leases [Abstract]
Operating lease expense	$ 109.6	$ 100.2	$ 103.6
Variable lease expense	20.4	18.8	16.6
Finance Leases
Amortization of right-of-use assets	7.6	5.2	6.9
Interest on lease liabilities	0.2	0.3	0.6
Total lease expense	$ 137.8	$ 124.5	$ 127.7