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INVESTMENTS - Investment Holdings (Details) - USD ($) $ in Thousands | 9 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2023 | Mar. 31, 2023
Summary of Investment Holdings [Line Items] |  |  |
Cost | $ 868,504 | $ 720,630 | [1]
Fair Value | 902,808 | 753,543 | [1]
South |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | 326,849 | 171,056 |
West |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | 228,407 | 197,989 |
Northeast |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | 213,403 | 266,612 |
Midwest |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | 134,149 | 117,886 |
Diversified/Conglomerate Services |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | 255,141 | 268,954 |
Home and Office Furnishings, Housewares, and Durable Consumer Products |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | 155,897 | 143,685 |
Machinery (Non-Agriculture, Non-Construction, and Non-Electronic) |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | 92,293 | 20,088 |
Hotels, Motels, Inns, and Gaming |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | 80,557 | 58,713 |
Buildings and Real Estate |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | 64,352 | 60,571 |
Healthcare, Education, and Childcare |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | 50,237 | 37,445 |
Oil and Gas |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | 45,983 | 0 |
Leisure, Amusement, Motion Pictures, and Entertainment |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | 38,356 | 47,616 |
Mining, Steel, Iron and Non-Precious Metals |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | 27,831 | 25,998 |
Aerospace and Defense |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | 25,754 | 22,215 |
Chemicals, Plastics, and Rubber |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | 19,256 | 24,891 |
Printing and Publishing |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | 15,210 | 0 |
Cargo Transport |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | 13,500 | 14,707 |
Telecommunications |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | 8,881 | 18,987 |
Other |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | $ 9,560 | $ 9,673 |
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 | Industry Concentration Risk | Diversified/Conglomerate Services |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 28.30% | 35.70% |
Investment Owned, At Fair Value | Industry Concentration Risk | Home and Office Furnishings, Housewares, and Durable Consumer Products |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 17.30% | 19.10% |
Investment Owned, At Fair Value | Industry Concentration Risk | Machinery (Non-Agriculture, Non-Construction, and Non-Electronic) |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 10.20% | 2.70% |
Investment Owned, At Fair Value | Industry Concentration Risk | Hotels, Motels, Inns, and Gaming |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 8.90% | 7.80% |
Investment Owned, At Fair Value | Industry Concentration Risk | Buildings and Real Estate |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 7.10% | 8.00% |
Investment Owned, At Fair Value | Industry Concentration Risk | Healthcare, Education, and Childcare |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 5.60% | 5.00% |
Investment Owned, At Fair Value | Industry Concentration Risk | Oil and Gas |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 5.10% | 0.00% |
Investment Owned, At Fair Value | Industry Concentration Risk | Leisure, Amusement, Motion Pictures, and Entertainment |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 4.20% | 6.30% |
Investment Owned, At Fair Value | Industry Concentration Risk | Mining, Steel, Iron and Non-Precious Metals |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 3.10% | 3.50% |
Investment Owned, At Fair Value | Industry Concentration Risk | Aerospace and Defense |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 2.90% | 2.80% |
Investment Owned, At Fair Value | Industry Concentration Risk | Chemicals, Plastics, and Rubber |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 2.10% | 3.30% |
Investment Owned, At Fair Value | Industry Concentration Risk | Printing and Publishing |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 1.70% | 0.00% |
Investment Owned, At Fair Value | Industry Concentration Risk | Cargo Transport |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 1.50% | 2.00% |
Investment Owned, At Fair Value | Industry Concentration Risk | Telecommunications |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 1.00% | 2.50% |
Investment Owned, At Fair Value | Industry Concentration Risk | Other |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 1.00% | 1.30% |
Investment Owned, At Fair Value | Geographic Regions Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 100.00% | 100.00% |
Investment Owned, At Fair Value | Geographic Regions Risk | South |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 36.20% | 22.70% |
Investment Owned, At Fair Value | Geographic Regions Risk | West |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 25.30% | 26.30% |
Investment Owned, At Fair Value | Geographic Regions Risk | Northeast |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 23.60% | 35.40% |
Investment Owned, At Fair Value | Geographic Regions Risk | Midwest |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 14.90% | 15.60% |
Debt Securities |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Cost | $ 665,697 | $ 555,597 |
Fair Value | $ 613,606 | $ 513,251 |
Debt Securities | Investment Owned, At Cost | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 76.60% | 77.10% |
Debt Securities | Investment Owned, At Fair Value | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 67.90% | 68.20% |
Secured First Lien Debt |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Cost | $ 517,539 | $ 471,439 |
Fair Value | $ 476,126 | $ 437,517 |
Secured First Lien Debt | Investment Owned, At Cost | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 59.60% | 65.40% |
Secured First Lien Debt | Investment Owned, At Fair Value | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 52.70% | 58.10% |
Secured Second Lien Debt |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Cost | $ 148,158 | $ 84,158 |
Fair Value | $ 137,480 | $ 75,734 |
Secured Second Lien Debt | Investment Owned, At Cost | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 17.00% | 11.70% |
Secured Second Lien Debt | Investment Owned, At Fair Value | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 15.20% | 10.10% |
Equity Securities |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Cost | $ 202,807 | $ 165,033 |
Fair Value | $ 289,202 | $ 240,292 |
Equity Securities | Investment Owned, At Cost | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 23.40% | 22.90% |
Equity Securities | Investment Owned, At Fair Value | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 32.10% | 31.80% |
Preferred Equity |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Cost | $ 151,969 | $ 149,099 |
Fair Value | $ 214,664 | $ 222,585 |
Preferred Equity | Investment Owned, At Cost | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 17.50% | 20.70% |
Preferred Equity | Investment Owned, At Fair Value | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 23.80% | 29.50% |
Common Equity/ Equivalents |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Cost | $ 50,838 | $ 15,934 |
Fair Value | $ 74,538 | $ 17,707 |
Common Equity/ Equivalents | Investment Owned, At Cost | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 5.90% | 2.20% |
Common Equity/ Equivalents | Investment Owned, At Fair Value | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 8.30% | 2.30% |
[1] | Cumulative gross unrealized appreciation for federal income tax purposes is $150.4 million; cumulative gross unrealized depreciation for federal income tax purposes is $119.3 million. Cumulative net unrealized appreciation is $31.1 million, based on a tax cost of $722.4 million.

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