Leases (Details) - USD ($)	3 Months Ended		6 Months Ended			12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2017	Sep. 30, 2019	Sep. 30, 2018
Leases [Abstract]
Lease, Cost	$ 9,800,000		$ 19,400,000
Operating Lease, Expense	7,000,000.0		13,800,000
Variable Lease, Cost	2,800,000		5,600,000
Operating Lease, Right-of-Use Asset	72,600,000		72,600,000
Operating Lease, Liability, Current	22,000,000.0		22,000,000.0
Operating Lease, Liability, Noncurrent	$ 55,200,000		$ 55,200,000
Lessee, Operating Lease, Discount Rate	3.30%		3.30%
Operating Lease, Weighted Average Remaining Lease Term	4 years 9 months 18 days		4 years 9 months 18 days
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year	$ 12,700,000		$ 12,700,000
Lessee, Operating Lease, Liability, Payments, Due Next Twelve Months	22,500,000		22,500,000
Lessee, Operating Lease, Liability, Payments, Due Year Two	17,200,000		17,200,000
Lessee, Operating Lease, Liability, Payments, Due Year Three	12,100,000		12,100,000
Lessee, Operating Lease, Liability, Payments, Due Year Four	7,300,000		7,300,000
Lessee, Operating Lease, Liability, Payments, Due Year Five	4,800,000		4,800,000
Lessee, Operating Lease, Liability, Payments, Due after Year Five	10,200,000		10,200,000
Lessee, Operating Lease, Liability, Payments, Due	86,800,000		86,800,000
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	(9,600,000)		(9,600,000)
Operating Lease, Liability	77,200,000		77,200,000
Operating Leases, Future Minimum Payments Receivable						$ 94,900,000
Operating Leases, Future Minimum Payments Receivable, Current						25,700,000
Operating Leases, Future Minimum Payments Receivable, in Two Years						21,400,000
Operating Leases, Future Minimum Payments Receivable, in Three Years						15,700,000
Operating Leases, Future Minimum Payments Receivable, in Four Years						11,100,000
Operating Leases, Future Minimum Payments Receivable, in Five Years						6,400,000
Operating Leases, Future Minimum Payments Receivable, Thereafter						14,600,000
Operating Leases, Rent Expense					$ 38,000,000.0	$ 39,800,000	$ 41,300,000
Rental expenses	38,500,000	$ 38,900,000	75,500,000	$ 76,100,000
Lessee, Lease, Description [Line Items]
Operating Lease, Expense	7,000,000.0		13,800,000
Variable Lease, Cost	$ 2,800,000		$ 5,600,000
Operating Lease, Weighted Average Remaining Lease Term	4 years 9 months 18 days		4 years 9 months 18 days