INVESTMENTS - Portfolio by Industry Grouping (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025
Investments, fair value	$ 569,202	$ 578,649
Percent of net assets	225.10%	222.70%
Investments Excluding STRS JV's
Investments, fair value	$ 460,585	$ 472,631
Percent of net assets	100.00%	100.00%
Investments Excluding STRS JV's \| Advertising
Investments, fair value	$ 14,655	$ 13,975
Percent of net assets	3.20%	3.00%
Investments Excluding STRS JV's \| Air Freight & Logistics
Investments, fair value	$ 9,388	$ 9,281
Percent of net assets	2.00%	2.00%
Investments Excluding STRS JV's \| Application Software
Investments, fair value	$ 29,912	$ 22,741
Percent of net assets	6.50%	4.80%
Investments Excluding STRS JV's \| Building Products
Investments, fair value	$ 1,329	$ 13,748
Percent of net assets	0.30%	2.90%
Investments Excluding STRS JV's \| Cargo Ground Transportation
Investments, fair value	$ 7,583	$ 7,701
Percent of net assets	1.60%	1.60%
Investments Excluding STRS JV's \| Construction & Engineering
Investments, fair value	$ 5,387	$ 9,906
Percent of net assets	1.20%	2.10%
Investments Excluding STRS JV's \| Diversified Chemicals
Investments, fair value	$ 13,642	$ 8,188
Percent of net assets	3.00%	1.70%
Investments Excluding STRS JV's \| Diversified Support Services
Investments, fair value	$ 16,420	$ 15,846
Percent of net assets	3.60%	3.40%
Investments Excluding STRS JV's \| Education Services
Investments, fair value	$ 25,239	$ 15,587
Percent of net assets	5.50%	3.30%
Investments Excluding STRS JV's \| Environmental & Facilities Services
Investments, fair value	$ 4,444	$ 3,255
Percent of net assets	1.00%	0.70%
Investments Excluding STRS JV's \| Food Distributors
Investments, fair value	$ 561	$ 264
Percent of net assets	0.10%	0.10%
Investments Excluding STRS JV's \| Health Care Facilities
Investments, fair value	$ 4,897	$ 4,623
Percent of net assets	1.10%	1.00%
Investments Excluding STRS JV's \| Health Care Services
Investments, fair value	$ 8,406	$ 8,389
Percent of net assets	1.80%	1.80%
Investments Excluding STRS JV's \| Health Care Supplies
Investments, fair value	$ 20,409	$ 20,026
Percent of net assets	4.40%	4.20%
Investments Excluding STRS JV's \| Home Furnishings
Investments, fair value	$ 18,089	$ 16,103
Percent of net assets	3.90%	3.40%
Investments Excluding STRS JV's \| Household Appliances
Investments, fair value	$ 911	$ 2,202
Percent of net assets	0.30%	0.50%
Investments Excluding STRS JV's \| Household Products
Investments, fair value	$ 7,785	$ 9,658
Percent of net assets	1.80%	2.00%
Investments Excluding STRS JV's \| Human Resource & Employment Services
Investments, fair value	$ 2,891	$ 2,909
Percent of net assets	0.60%	0.60%
Investments Excluding STRS JV's \| Industrial Machinery & Supplies & Components
Investments, fair value	$ 19,024	$ 12,895
Percent of net assets	4.10%	2.70%
Investments Excluding STRS JV's \| Integrated Telecommunication Services
Investments, fair value	$ 15,157	$ 26,732
Percent of net assets	3.30%	5.70%
Investments Excluding STRS JV's \| Interactive Media & Services
Investments, fair value	$ 15,818	$ 15,940
Percent of net assets	3.40%	3.40%
Investments Excluding STRS JV's \| IT Consulting & Other Services
Investments, fair value	$ 591	$ 1,287
Percent of net assets	0.10%	0.30%
Investments Excluding STRS JV's \| Leisure Facilities
Investments, fair value	$ 12,401	$ 15,233
Percent of net assets	2.70%	3.20%
Investments Excluding STRS JV's \| Leisure Products
Investments, fair value	$ 17,540	$ 16,672
Percent of net assets	3.80%	3.50%
Investments Excluding STRS JV's \| Office Services & Supplies
Investments, fair value	$ 15,880	$ 5,159
Percent of net assets	3.40%	1.10%
Investments Excluding STRS JV's \| Oil & Gas Refining & Marketing
Investments, fair value	$ 10,408	$ 10,404
Percent of net assets	2.30%	2.20%
Investments Excluding STRS JV's \| Oil & Gas Storage & Transportation
Investments, fair value	$ 10,266	$ 10,158
Percent of net assets	2.20%	2.10%
Investments Excluding STRS JV's \| Other Specialty Retail
Investments, fair value	$ 625	$ 735
Percent of net assets	0.10%	0.20%
Investments Excluding STRS JV's \| Packaged Foods & Meats
Investments, fair value	$ 3,626	$ 4,033
Percent of net assets	0.80%	0.90%
Investments Excluding STRS JV's \| Paper Products
Investments, fair value	$ 8,892	$ 9,276
Percent of net assets	1.90%	2.00%
Investments Excluding STRS JV's \| Pharmaceuticals
Investments, fair value		$ 12,027
Percent of net assets		2.50%
Investments Excluding STRS JV's \| Real Estate Services
Investments, fair value	$ 9,380	$ 20,426
Percent of net assets	2.00%	4.30%
Investments Excluding STRS JV's \| Research & Consulting Services
Investments, fair value	$ 5,115	$ 5,143
Percent of net assets	1.20%	1.10%
Investments Excluding STRS JV's \| Specialized Consumer Services
Investments, fair value	$ 29,541	$ 26,556
Percent of net assets	6.40%	5.60%
Investments Excluding STRS JV's \| Specialized Finance
Investments, fair value	$ 10,307	$ 10,661
Percent of net assets	2.20%	2.30%
Investments Excluding STRS JV's \| Systems Software
Investments, fair value	$ 28,430	$ 28,504
Percent of net assets	6.20%	6.00%
Investments Excluding STRS JV's \| Technology Hardware, Storage & Peripherals
Investments, fair value	$ 19,490	$ 19,484
Percent of net assets	4.20%	4.10%
Investments Excluding STRS JV's \| Transaction & Payment Processing Services
Investments, fair value	$ 36,146	$ 36,904
Percent of net assets	7.80%	7.80%