Leases - Maturities of Lease Liabilities (Details) $ in Millions	Mar. 31, 2021 USD ($)	Sep. 30, 2019 building
Financing
2021	$ 1.5
2022	3.0
2023	2.8
2024	2.7
2025	2.7
Thereafter	0.7
Total lease payments	13.4
Less: imputed interest	(0.5)
Present value of financing lease liabilities	12.9
Operating
2021	8.3
2022	16.9
2023	14.9
2024	13.9
2025	11.5
Thereafter	37.9
Total lease payments	103.4
Less: imputed interest	(10.8)
Present value of operating lease liabilities	$ 92.6
Number of buildings | building		2
Lease term		5 years