CONSOLIDATED STATEMENTS OF CHANGES IN NET ASSETS (Parentheticals) - $ / shares	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Statement of Stockholders' Equity [Abstract]
Net investment income (in USD per share)	$ 1.98	$ 1.89	$ 1.52	$ 1.50	$ 1.60	$ 1.64	$ 1.68	$ 1.68	$ 1.40	$ 1.68
Return of capital (in USD per share)	$ 0.00	$ 0.00	$ 0.08	$ 0.06	$ 0.02	$ 0.04	$ 0	$ 0	$ 0	$ 0