Leases - Components of Lease Expense (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Mar. 31, 2020	Mar. 31, 2020
Leases [Abstract]
Operating lease expense	$ 25.7	$ 51.0
Variable lease expense	3.6	7.5
Total lease expense	$ 29.3	$ 58.5