Fair Value of Financial Instruments - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Net unrealized appreciation (depreciation) on investments and debt	$ 51,398	$ 12,290	$ (10,141)
Truist Credit Facility
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Line of credit facility amendment costs	300	0	0
Net change in unrealized appreciation (depreciation)	(100)	(4,400)	(3,800)
Net unrealized appreciation (depreciation) on investments and debt	$ (1,000)	$ (1,100)	$ (5,500)