Leases - Summary of Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$ (19.1)
Operating cash flows from finance leases	(0.2)
Repayments of finance lease obligations	(6.3)	$ (4.1)
Non-cash items:
Right-of-use Assets Obtained In Exchange For New Operating Liabilities	11.7
Right-of-use Assets Obtained In Exchange For New Finance Liabilities	$ 15.8