Leases - Summary of Supplemental Cash Flow Information Related to Leases (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Cash Paid For Amounts Included In Measurement Of Lease Obligations [Abstract]
Operating cash flows from operating leases	$ 26.2	$ 24.4
Operating cash flows from finance leases	0.2	0.1
Financing cash flows from finance leases	1.5	0.6
Right-of-use assets obtained in exchange for new finance lease liabilities	6.3	1.7
Right-of-use assets obtained in exchange for new operating lease liabilities	$ 10.8	$ 4.5