Leases - Additional Information (Details)	12 Months Ended
	Sep. 30, 2022 USD ($) ft²	Mar. 31, 2022 USD ($)	Sep. 30, 2021 USD ($)	Feb. 28, 2019 USD ($)
Lessee Lease Description [Line Items]
Boston Lease Square Feet | ft²	250,000
Boston lease year one payments	$ 11,000,000.0
Boston lease per square foot annual increase	1
Boston lease annual increase	300,000
Boston lease building operating cost amount estimate year one	7,100,000
Boston lease leasehold improvement allowance	25,000,000
Boston lease leasehold improvement allowance per square foot	100
Future lease payments	11,600,000
Operating right-of-use lease assets	137,780,000		$ 152,337,000
Operating lease, liability	189,575,000
Payments to be received as sublease income		$ 2,900,000		$ 9,100,000
Lease Cost
Operating cash flows from operating leases	$ 38,709,000
Minimum
Lessee Lease Description [Line Items]
Leases not yet commenced, Term of contract	10 years
Facility Closures and Related Costs
Lessee Lease Description [Line Items]
Operating lease liability, net. restructured facilities	$ 300,000		$ 3,600,000
Lease Cost
Operating cash flows from operating leases	2,000,000.0
Facility Closures and Related Costs | Prior Headquarters
Lessee Lease Description [Line Items]
Operating lease, impairment loss	1,300,000
Sublease Income Committed
Lessee Lease Description [Line Items]
Sublease income assumed	0
Sublease Income Estimated Uncommitted
Lessee Lease Description [Line Items]
Sublease income assumed	$ 0