Leases - Summary of Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$ 23.6	$ 25.3
Operating cash flows from finance leases	(0.7)	(0.3)
Financing cash flows from finance leases	20.5	9.9	$ 5.8
Non-cash items:
Right-of-use Assets Obtained In Exchange For New Operating Liabilities	33.8	17.1
Right-of-use Assets Obtained In Exchange For New Finance Liabilities	$ 22.0	$ 20.2