INVESTMENTS - Selected Statement of Operations Information For STRS JV (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Schedule of Investments [Line Items]
Total investment income	$ 21,558	$ 18,378	$ 61,592	$ 53,689
Administrative service fees	171	171	512	512
Total expenses	11,595	10,486	34,814	31,508
Net investment income after excise tax	9,768	7,639	26,184	21,336
Net increase in net assets resulting from operations	3,845	8,275	16,901	26,951
STRS JV
Schedule of Investments [Line Items]
Interest income	7,858	4,972	20,985	13,554
Total investment income	7,858	4,972	20,985	13,554
Interest expense on credit facility	2,034	1,079	4,919	3,037
Interest expense on notes to members	2,630	1,511	6,611	3,937
Administrative service fees	161	117	475	312
Other expenses	128	150	513	379
Total expenses	4,953	2,857	12,518	7,665
Net investment income after excise tax	2,905	2,115	8,467	5,889
Net realized gains (losses) on investments and foreign currency transactions	130	8	250	(51)
Net change in unrealized appreciation (depreciation) on investments and foreign currency transactions	(286)	874	1,306	1,209
Net increase in net assets resulting from operations	$ 2,749	$ 2,997	$ 10,023	$ 7,047