Commitments and Contingencies - Narrative (Details)	1 Months Ended	12 Months Ended
	Oct. 31, 2018	Sep. 30, 2019 USD ($) Letter_of_credit	Sep. 30, 2018 USD ($) Letter_of_credit	Sep. 30, 2017 USD ($)
Loss Contingencies [Line Items]
Lease term	24 months
Amortization period	7 years
Interest rate on lease obligation	560.00%
Rent expense under operating leases		$ 4,240,000	$ 4,149,000	$ 4,257,000
Sublease income under operating subleases		$ 51,000	$ 558,000	167,000
Number of letters of credit | Letter_of_credit		1	2
Litigation expense		$ 3,008,000	$ 1,737,000	3,414,000
Pending Litigation | Professional Fees
Loss Contingencies [Line Items]
Litigation and FINRA related expenses		2,052,000	950,000	$ 1,476,000
Pending Litigation | Accounts Payable and Accrued Expenses
Loss Contingencies [Line Items]
Estimate of possible loss		1,817,000	825,000
Letter of Credit
Loss Contingencies [Line Items]
Maximum borrowing capacity		$ 960,000	$ 1,353,000