Leases - Lease Expense (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Leases
Operating lease expense	$ 4.9	$ 4.6
Finance lease expense Amortization of right-of-use asset	0.1
Short-term lease expense		0.4
Variable lease expense	0.9	1.1
Total lease expense	$ 5.9	$ 6.1