Federal Income Tax Matters - Schedule of Accumulated Earnings (Deficit) Book Basis, Income Tax (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Schedule of Investments [Abstract]
Undistributed ordinary income – tax basis	$ 0	$ 19,151	$ 56,886
Undistributed realized gains – tax basis	0	0	0
Net unrealized appreciation (depreciation) on investments	9,860	(155,498)	(160,673)
Other temporary differences	(58,676)	(16,646)	4,583
Total accumulated earnings (deficit) – book basis	$ (48,816)	$ (152,993)	$ (99,204)