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INVESTMENTS - Summary Investment Holdings (Details) - USD ($) $ in Thousands | 6 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2025 | Sep. 30, 2024
Summary of Investment Holdings [Line Items] |  |  |
Cost | $ 789,193 | $ 771,011 | [1]
Fair Value | $ 762,636 | $ 796,260 | [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 | $ 250,685 | $ 314,010 |
South | Investment Owned, At Fair Value | Geographic Regions Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 32.90% | 39.40% |
West |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | $ 243,031 | $ 249,082 |
West | Investment Owned, At Fair Value | Geographic Regions Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 31.80% | 31.30% |
Midwest |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | $ 215,704 | $ 192,897 |
Midwest | Investment Owned, At Fair Value | Geographic Regions Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 28.30% | 24.20% |
Northeast |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | $ 53,216 | $ 40,271 |
Northeast | Investment Owned, At Fair Value | Geographic Regions Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 7.00% | 5.10% |
Healthcare, Education, and Childcare |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | $ 218,439 | $ 101,707 |
Healthcare, Education, and Childcare | Investment Owned, At Fair Value | Industry Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 28.60% | 12.80% |
Diversified/Conglomerate Manufacturing |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | $ 177,211 | $ 160,264 |
Diversified/Conglomerate Manufacturing | Investment Owned, At Fair Value | Industry Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 23.20% | 20.10% |
Diversified/Conglomerate Service |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | $ 95,686 | $ 179,032 |
Diversified/Conglomerate Service | Investment Owned, At Fair Value | Industry Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 12.50% | 22.50% |
Beverage, Food, and Tobacco |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | $ 92,901 | $ 88,327 |
Beverage, Food, and Tobacco | Investment Owned, At Fair Value | Industry Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 12.20% | 11.10% |
Aerospace and Defense |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | $ 59,193 | $ 153,096 |
Aerospace and Defense | Investment Owned, At Fair Value | Industry Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 7.80% | 19.20% |
Automobile |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | $ 27,954 | $ 28,286 |
Automobile | Investment Owned, At Fair Value | Industry Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 3.70% | 3.60% |
Machinery |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | $ 22,956 | $ 21,816 |
Machinery | Investment Owned, At Fair Value | Industry Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 3.00% | 2.70% |
Cargo Transportation |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | $ 20,200 | $ 20,200 |
Cargo Transportation | Investment Owned, At Fair Value | Industry Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 2.70% | 2.50% |
Oil and Gas |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | $ 19,358 | $ 20,554 |
Oil and Gas | Investment Owned, At Fair Value | Industry Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 2.50% | 2.60% |
Personal and Non-Durable Consumer Products |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | $ 12,618 | $ 13,586 |
Personal and Non-Durable Consumer Products | Investment Owned, At Fair Value | Industry Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 1.70% | 1.70% |
Printing and Publishing |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | $ 5,515 | $ 4,312 |
Printing and Publishing | Investment Owned, At Fair Value | Industry Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 0.70% | 0.50% |
Other |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Fair Value | $ 10,605 | $ 5,080 |
Other | Investment Owned, At Fair Value | Industry Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 1.40% | 0.70% |
Debt Securities |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Cost | $ 719,963 | $ 694,625 |
Fair Value | $ 686,829 | $ 668,685 |
Debt Securities | Investment Owned, At Cost | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 91.20% | 90.10% |
Debt Securities | Investment Owned, At Fair Value | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 90.10% | 84.00% |
Secured first lien debt |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Cost | $ 574,590 | $ 580,736 |
Fair Value | $ 541,524 | $ 554,937 |
Secured first lien debt | Investment Owned, At Cost | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 72.80% | 75.30% |
Secured first lien debt | Investment Owned, At Fair Value | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 71.00% | 69.70% |
Secured second lien debt |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Cost | $ 144,842 | $ 113,691 |
Fair Value | $ 144,970 | $ 113,716 |
Secured second lien debt | Investment Owned, At Cost | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 18.30% | 14.80% |
Secured second lien debt | Investment Owned, At Fair Value | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 19.00% | 14.30% |
Unsecured debt |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Cost | $ 531 | $ 198 |
Fair Value | $ 335 | $ 32 |
Unsecured debt | Investment Owned, At Cost | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 0.10% | 0.00% |
Unsecured debt | Investment Owned, At Fair Value | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 0.10% | 0.00% |
Equity Securities |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Cost | $ 69,230 | $ 76,386 |
Fair Value | $ 75,807 | $ 127,575 |
Equity Securities | Investment Owned, At Cost | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 8.80% | 9.90% |
Equity Securities | Investment Owned, At Fair Value | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 9.90% | 16.00% |
Preferred Equity |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Cost | $ 37,279 | $ 45,017 |
Fair Value | $ 25,031 | $ 31,346 |
Preferred Equity | Investment Owned, At Cost | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 4.70% | 5.80% |
Preferred Equity | Investment Owned, At Fair Value | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 3.30% | 3.90% |
Common Equity/ Equivalents |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Cost | $ 31,951 | $ 31,369 |
Fair Value | $ 50,776 | $ 96,229 |
Common Equity/ Equivalents | Investment Owned, At Cost | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 4.10% | 4.10% |
Common Equity/ Equivalents | Investment Owned, At Fair Value | Investment Type Concentration Risk |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Concentration risk, percentage | 6.60% | 12.10% |
[1] | Cumulative gross unrealized depreciation for federal income tax purposes is $66.1 million; cumulative gross unrealized appreciation for federal income tax purposes is $85.8 million. Cumulative net unrealized appreciation is $19.7 million, based on a tax cost of $776.5 million.

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