Income Taxes - Reconciliation of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Expected U.S. federal income taxes at statutory rate	$ (809)	$ (3,824)	$ (1,519)
Partnership income not taxed at federal level	865	1,035	29
Valuation allowance	(3,964)	7,101	712
State and local income taxes, net of federal benefit	2,451	(641)	552
Nondeductible expenses and other permanent items	189	83	85
Revaluation of debt and other debt transaction differences	536	1,434	609
Change in liability for uncertain tax positions	155	(25)	(83)
Federal tax credits	(636)	0	240
Other	10	(156)	(2)
Income tax (benefit) expense	$ (1,203)	$ 5,007	$ 623
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Expected U.S. federal income taxes at statutory rate	21.00%	21.00%	21.10%
Partnership income not taxed at federal level	(22.40%)	(5.70%)	(0.40%)
Valuation allowance	102.80%	(39.00%)	(9.90%)
State and local income taxes, net of federal benefit	(63.60%)	3.50%	(7.60%)
Nondeductible expenses and other permanent items	(4.90%)	(0.50%)	(1.20%)
Revaluation of debt and other debt transaction differences	(0.139)	(0.079)	(0.084)
Change in liability for uncertain tax positions	(4.00%)	0.10%	1.20%
Federal tax credits	16.50%	0.00%	(3.30%)
Other	(0.30%)	0.90%	0.00%
Income tax (benefit) expense	31.20%	(27.50%)	(8.60%)