Leases - Summary of Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Mar. 31, 2020	Mar. 31, 2020	Mar. 31, 2019
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$ (6.4)	$ (13.0)
Operating cash flows from finance leases		(0.1)
Repayments of finance lease obligations	(1.7)	(3.2)	$ (2.8)
Non-cash items:
New finance leases	$ 3.2	$ 3.2