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INVESTMENTS - Summary Investment Holdings (Details) - USD ($) $ in Thousands | 6 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2022 | Mar. 31, 2022
Summary of Investment Holdings [Line Items] |  |  |
Cost | $ 703,218 | $ 669,248 | [1]
Fair Value | $ 737,935 | $ 714,396 | [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% |
West |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | $ 236,774 | $ 158,607 |
West | Investment Owned, At Fair Value | Geographic Regions Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 32.10% | 22.20% |
Northeast |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | $ 218,107 | $ 194,100 |
Northeast | Investment Owned, At Fair Value | Geographic Regions Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 29.60% | 27.20% |
South |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | $ 172,784 | $ 188,978 |
South | Investment Owned, At Fair Value | Geographic Regions Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 23.40% | 26.40% |
Midwest |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | $ 110,270 | $ 172,711 |
Midwest | Investment Owned, At Fair Value | Geographic Regions Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 14.90% | 24.20% |
Diversified/Conglomerate Services |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | $ 267,913 | $ 307,403 |
Diversified/Conglomerate Services | Investment Owned, At Fair Value | Industry Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 36.30% | 43.00% |
Home and Office Furnishings, Housewares, and Durable Consumer Products |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | $ 133,359 | $ 125,440 |
Home and Office Furnishings, Housewares, and Durable Consumer Products | Investment Owned, At Fair Value | Industry Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 18.10% | 17.60% |
Buildings and Real Estate |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | $ 60,050 | $ 0 |
Buildings and Real Estate | Investment Owned, At Fair Value | Industry Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 8.10% | 0.00% |
Hotels, Motels, Inns, and Gaming |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | $ 53,090 | $ 37,923 |
Hotels, Motels, Inns, and Gaming | Investment Owned, At Fair Value | Industry Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 7.20% | 5.30% |
Leisure, Amusement, Motion Pictures, and Entertainment |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | $ 45,169 | $ 46,514 |
Leisure, Amusement, Motion Pictures, and Entertainment | Investment Owned, At Fair Value | Industry Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 6.10% | 6.50% |
Healthcare, Education, and Childcare |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | $ 38,937 | $ 39,252 |
Healthcare, Education, and Childcare | Investment Owned, At Fair Value | Industry Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 5.30% | 5.50% |
Aerospace and Defense |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | $ 23,746 | $ 25,296 |
Aerospace and Defense | Investment Owned, At Fair Value | Industry Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 3.20% | 3.50% |
Chemicals, Plastics, and Rubber |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | $ 23,642 | $ 26,618 |
Chemicals, Plastics, and Rubber | Investment Owned, At Fair Value | Industry Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 3.20% | 3.70% |
Mining, Steel, Iron and Non-Precious Metals |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | $ 23,368 | $ 24,250 |
Mining, Steel, Iron and Non-Precious Metals | Investment Owned, At Fair Value | Industry Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 3.20% | 3.40% |
Telecommunications |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | $ 23,200 | $ 32,467 |
Telecommunications | Investment Owned, At Fair Value | Industry Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 3.10% | 4.60% |
Machinery (Non-Agriculture, Non-Construction, and Non-Electronic) |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | $ 17,407 | $ 13,823 |
Machinery (Non-Agriculture, Non-Construction, and Non-Electronic) | Investment Owned, At Fair Value | Industry Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 2.40% | 1.90% |
Cargo Transport |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | $ 14,827 | $ 14,533 |
Cargo Transport | Investment Owned, At Fair Value | Industry Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 2.00% | 2.00% |
Diversified/Conglomerate Manufacturing |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | $ 9,259 | $ 14,064 |
Diversified/Conglomerate Manufacturing | Investment Owned, At Fair Value | Industry Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 1.30% | 2.00% |
Other |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | $ 3,968 | $ 6,813 |
Other | Investment Owned, At Fair Value | Industry Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 0.50% | 1.00% |
Debt Securities |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Cost | $ 538,563 | $ 510,604 |
Fair Value | $ 497,658 | $ 493,045 |
Debt Securities | Investment Owned, At Cost | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 76.60% | 76.30% |
Debt Securities | Investment Owned, At Fair Value | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 67.40% | 69.00% |
Secured First Lien Debt |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Cost | $ 444,089 | $ 429,457 |
Fair Value | $ 420,907 | $ 425,087 |
Secured First Lien Debt | Investment Owned, At Cost | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 63.20% | 64.20% |
Secured First Lien Debt | Investment Owned, At Fair Value | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 57.00% | 59.50% |
Secured Second Lien Debt |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Cost | $ 94,474 | $ 81,147 |
Fair Value | $ 76,751 | $ 67,958 |
Secured Second Lien Debt | Investment Owned, At Cost | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 13.40% | 12.10% |
Secured Second Lien Debt | Investment Owned, At Fair Value | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 10.40% | 9.50% |
Equity Securities |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Cost | $ 164,655 | $ 158,644 |
Fair Value | $ 240,277 | $ 221,351 |
Equity Securities | Investment Owned, At Cost | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 23.40% | 23.70% |
Equity Securities | Investment Owned, At Fair Value | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 32.60% | 31.00% |
Preferred Equity |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Cost | $ 149,099 | $ 143,079 |
Fair Value | $ 229,430 | $ 217,599 |
Preferred Equity | Investment Owned, At Cost | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 21.20% | 21.40% |
Preferred Equity | Investment Owned, At Fair Value | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 31.10% | 30.50% |
Common Equity/ Equivalents |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Cost | $ 15,556 | $ 15,565 |
Fair Value | $ 10,847 | $ 3,752 |
Common Equity/ Equivalents | Investment Owned, At Cost | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 2.20% | 2.30% |
Common Equity/ Equivalents | Investment Owned, At Fair Value | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 1.50% | 0.50% |
[1] | Cumulative gross unrealized appreciation for federal income tax purposes is $140.8 million; cumulative gross unrealized depreciation for federal income tax purposes is $97.1 million. Cumulative net unrealized appreciation is $43.8 million, based on a tax cost of $670.6 million.

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