Credit Facilities - Summary of Loan Facilities and Subordinated Debt Financing (Details) - Secured Debt - USD ($)	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Debt Instrument [Line Items]
Loan Balance	$ 46,750,000	$ 70,000,000
Secured term loan
Debt Instrument [Line Items]
Loan Balance	$ 46,800,000
Secured term loan | LIBOR
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	0.035%
Debt instrument, interest rate, effective percentage	0.08%
Debt instrument, floor percentage		0.50%
Secured revolving line of credit
Debt Instrument [Line Items]
Loan Balance	$ 0
Secured revolving line of credit | LIBOR
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	0.035%
Debt instrument, interest rate, effective percentage	0.08%
Debt instrument, floor percentage		0.50%