Leases - Additional Information (Details) $ in Thousands	1 Months Ended	3 Months Ended		12 Months Ended
	Dec. 31, 2014 USD ($)	Sep. 30, 2020 USD ($)	Mar. 31, 2015 USD ($)	Sep. 30, 2020 USD ($) extension_option	Sep. 30, 2018	Oct. 01, 2019 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)
Lessee, Lease, Description [Line Items]
Weighted average remaining lease term for operating leases (in years)		5 years 2 months 12 days		5 years 2 months 12 days
Weighted average incremental borrowing rate used to measure lease liabilities		7.37%		7.37%
Right-of-use asset		$ 183,809		$ 183,809		$ 246,028
Operating lease, liability		$ 202,782		$ 202,782		246,028
Initial term of lease (in years)		10 years		10 years
Estimated minimum future rental payments		$ 246,168		$ 246,168
Impairment charges		$ 5,000
Operating lease right of use asset non cash				29,200
Operating lease liability non cash				$ 29,200
Revision of Prior Period, Error Correction, Adjustment
Lessee, Lease, Description [Line Items]
Right-of-use asset						(18,000)
Operating lease, liability						$ (18,000)
Corporate Office Lease, Two Five-Year Extension Options
Lessee, Lease, Description [Line Items]
Initial term of lease (in years)	13 years
Annual rent at lease inception	$ 2,500
Annual rent in the terminal year of lease	$ 3,900
Number of extension options | extension_option				2
Renewable term of lease (in years)		5 years		5 years
Estimated minimum future rental payments		$ 38,100		$ 38,100
Estimated future minimum sublease payments							$ 12,200	$ 12,200
Initial leased premises surrendered					15.00%
Regional Offices Sublease
Lessee, Lease, Description [Line Items]
Estimated future minimum sublease payments			$ 2,900
Sublease term (in years)			9 years