Leases - Operating Lease Costs and Other Related Information (Details) $ in Millions	12 Months Ended
	Sep. 30, 2020 USD ($)
Leases [Abstract]
Operating lease costs	$ 17.2
Cash paid for amounts included in the measurement of operating lease liabilities	12.1
Right-of-use assets obtained in exchange for operating lease liabilities	$ 96.4
Weighted average remaining lease term (years)	11 years 3 months 18 days
Weighted average discount rate	4.30%