Leases - Summary of Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$ 28.9	$ 27.9
Operating cash flows from finance leases	1.6	1.0
Financing cash flows from finance leases	27.6	27.0	$ 20.5
Non-cash items:
Right-of-use Assets Obtained In Exchange For New Operating Liabilities	33.4	39.6
Right-of-use Assets Obtained In Exchange For New Finance Liabilities	$ 26.3	$ 33.3