Leases - Additional cash flow information (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$ 50.8	$ 57.8
Operating cash flows from finance leases	0.5	0.7
Financing cash flows from finance leases	4.3	1.9
Right-of-use assets obtained in exchange for new operating leases	14.7	42.6
Right-of-use assets obtained in exchange for new finance leases	$ 7.9	$ 8.4