Leases - Summary of Components of Lease Cost for Operating and Finance Leases (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Leases [Abstract]
Operating lease cost	$ 29.2	$ 25.3
Finance lease cost:
Amortization of right-of-use asset	20.2	17.1
Interest on lease liabilities	1.0	0.8
Total finance lease cost	21.2	17.9
Short-term lease cost	22.0	18.4
Variable lease costs not included in lease liability	2.9	2.4
Sublease income	(0.6)	(0.5)
Total lease cost	$ 74.7	$ 63.5