Leases - Components of Lease Expense (Details) $ in Millions	3 Months Ended
	Dec. 31, 2019 USD ($)
Leases [Abstract]
Operating lease cost	$ 25.6
Finance lease cost:
Amortization of ROU assets	1.6
Interest on lease liabilities	0.5
Variable lease cost	1.4
Short-term lease cost	1.0
Total lease cost	30.1
Cash paid related to lease liabilities:
Operating cash flows from operating leases	25.5
Operating cash flows from finance leases	0.5
Financing cash flows from finance leases	1.0
Non-cash lease liability activities:
ROU assets obtained in exchange for operating lease liabilities	451.9
ROU assets obtained in exchange for finance lease liabilities	$ 21.5
Weighted-average remaining lease term
Operating leases	6 years 3 months 18 days
Finance leases	2 years 6 months
Weighted-average discount rate
Operating leases	3.90%
Finance leases	2.00%