Quarterly report pursuant to Section 13 or 15(d)

INVESTMENTS - Summary Investment Holdings (Details)

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INVESTMENTS - Summary Investment Holdings (Details) - USD ($)
$ in Thousands
 3 Months Ended 12 Months Ended
Dec. 31, 2023
Sep. 30, 2023
Summary of Investment Holdings [Line Items]    
Cost $ 759,634 $ 722,269 [1]
Fair Value $ 749,985 $ 704,815 [1]
Investment Owned, At Cost | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration risk, percentage 100.00% 100.00%
Investment Owned, At Fair Value | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration risk, percentage 100.00% 100.00%
Investment Owned, At Fair Value | Industry Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration risk, percentage 100.00% 100.00%
Investment Owned, At Fair Value | Geographic Regions Risk    
Summary of Investment Holdings [Line Items]    
Concentration risk, percentage 100.00% 100.00%
South    
Summary of Investment Holdings [Line Items]    
Fair Value $ 289,458 $ 273,181
South | Investment Owned, At Fair Value | Geographic Regions Risk    
Summary of Investment Holdings [Line Items]    
Concentration risk, percentage 38.60% 38.80%
West    
Summary of Investment Holdings [Line Items]    
Fair Value $ 242,651 $ 224,235
West | Investment Owned, At Fair Value | Geographic Regions Risk    
Summary of Investment Holdings [Line Items]    
Concentration risk, percentage 32.40% 31.80%
Midwest    
Summary of Investment Holdings [Line Items]    
Fair Value $ 154,155 $ 145,122
Midwest | Investment Owned, At Fair Value | Geographic Regions Risk    
Summary of Investment Holdings [Line Items]    
Concentration risk, percentage 20.50% 20.60%
Northeast    
Summary of Investment Holdings [Line Items]    
Fair Value $ 63,721 $ 62,277
Northeast | Investment Owned, At Fair Value | Geographic Regions Risk    
Summary of Investment Holdings [Line Items]    
Concentration risk, percentage 8.50% 8.80%
Diversified/Conglomerate Service    
Summary of Investment Holdings [Line Items]    
Fair Value $ 163,817 $ 135,060
Diversified/Conglomerate Service | Investment Owned, At Fair Value | Industry Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration risk, percentage 21.80% 19.20%
Healthcare, Education, and Childcare    
Summary of Investment Holdings [Line Items]    
Fair Value $ 159,410 $ 146,438
Healthcare, Education, and Childcare | Investment Owned, At Fair Value | Industry Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration risk, percentage 21.30% 20.80%
Diversified/Conglomerate Manufacturing    
Summary of Investment Holdings [Line Items]    
Fair Value $ 158,612 $ 158,061
Diversified/Conglomerate Manufacturing | Investment Owned, At Fair Value | Industry Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration risk, percentage 21.10% 22.40%
Aerospace and Defense    
Summary of Investment Holdings [Line Items]    
Fair Value $ 105,806 $ 97,836
Aerospace and Defense | Investment Owned, At Fair Value | Industry Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration risk, percentage 14.10% 13.90%
Beverage, Food, and Tobacco    
Summary of Investment Holdings [Line Items]    
Fair Value $ 80,492 $ 78,788
Beverage, Food, and Tobacco | Investment Owned, At Fair Value | Industry Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration risk, percentage 10.70% 11.20%
Oil and Gas    
Summary of Investment Holdings [Line Items]    
Fair Value $ 23,662 $ 27,830
Oil and Gas | Investment Owned, At Fair Value | Industry Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration risk, percentage 3.20% 3.90%
Automobile    
Summary of Investment Holdings [Line Items]    
Fair Value $ 27,793 $ 27,571
Automobile | Investment Owned, At Fair Value | Industry Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration risk, percentage 3.70% 3.90%
Personal and Non-Durable Consumer Products    
Summary of Investment Holdings [Line Items]    
Fair Value $ 14,162 $ 14,576
Personal and Non-Durable Consumer Products | Investment Owned, At Fair Value | Industry Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration risk, percentage 1.90% 2.10%
Machinery    
Summary of Investment Holdings [Line Items]    
Fair Value $ 6,216 $ 6,411
Machinery | Investment Owned, At Fair Value | Industry Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration risk, percentage 0.90% 0.90%
Other    
Summary of Investment Holdings [Line Items]    
Fair Value $ 10,015 $ 12,244
Other | Investment Owned, At Fair Value | Industry Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration risk, percentage 1.30% 1.70%
Debt Securities    
Summary of Investment Holdings [Line Items]    
Cost $ 688,192 $ 659,826
Fair Value $ 673,196 $ 638,579
Debt Securities | Investment Owned, At Cost | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration risk, percentage 90.60% 91.40%
Debt Securities | Investment Owned, At Fair Value | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration risk, percentage 89.80% 90.60%
Secured first lien debt    
Summary of Investment Holdings [Line Items]    
Cost $ 558,281 $ 529,376
Fair Value $ 546,602 $ 510,701
Secured first lien debt | Investment Owned, At Cost | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration risk, percentage 73.50% 73.30%
Secured first lien debt | Investment Owned, At Fair Value | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration risk, percentage 72.90% 72.50%
Secured second lien debt    
Summary of Investment Holdings [Line Items]    
Cost $ 129,713 $ 130,252
Fair Value $ 126,571 $ 127,854
Secured second lien debt | Investment Owned, At Cost | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration risk, percentage 17.10% 18.10%
Secured second lien debt | Investment Owned, At Fair Value | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration risk, percentage 16.90% 18.10%
Unsecured debt    
Summary of Investment Holdings [Line Items]    
Cost $ 198 $ 198
Fair Value $ 23 $ 24
Unsecured debt | Investment Owned, At Cost | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration risk, percentage 0.00% 0.00%
Unsecured debt | Investment Owned, At Fair Value | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration risk, percentage 0.00% 0.00%
Equity Securities    
Summary of Investment Holdings [Line Items]    
Cost $ 71,442 $ 62,443
Fair Value $ 76,789 $ 66,236
Equity Securities | Investment Owned, At Cost | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration risk, percentage 9.40% 8.60%
Equity Securities | Investment Owned, At Fair Value | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration risk, percentage 10.20% 9.40%
Preferred Equity    
Summary of Investment Holdings [Line Items]    
Cost $ 44,617 $ 35,617
Fair Value $ 29,722 $ 26,855
Preferred Equity | Investment Owned, At Cost | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration risk, percentage 5.90% 4.90%
Preferred Equity | Investment Owned, At Fair Value | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration risk, percentage 3.90% 3.80%
Common Equity/ Equivalents    
Summary of Investment Holdings [Line Items]    
Cost $ 26,825 $ 26,826
Fair Value $ 47,067 $ 39,381
Common Equity/ Equivalents | Investment Owned, At Cost | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration risk, percentage 3.50% 3.70%
Common Equity/ Equivalents | Investment Owned, At Fair Value | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration risk, percentage 6.30% 5.60%
[1] Investment was exited subsequent to December 31, 2023. Refer to Note 12 – Subsequent Events in the accompanying Notes to the Consolidated Financial Statements for additional information.