Quarterly report [Sections 13 or 15(d)]

INVESTMENTS - Schedule of Investment Holdings (Details)

v3.26.1
INVESTMENTS - Schedule of Investment Holdings (Details) - USD ($)
$ in Thousands
 6 Months Ended 12 Months Ended
Mar. 31, 2026
Sep. 30, 2025
Summary of Investment Holdings [Line Items]    
Cost $ 925,193 $ 876,614 [1]
Fair Value 906,844 859,124 [1]
South    
Summary of Investment Holdings [Line Items]    
Fair Value 325,853 287,371
West    
Summary of Investment Holdings [Line Items]    
Fair Value 233,167 233,564
Midwest    
Summary of Investment Holdings [Line Items]    
Fair Value 221,458 237,417
Northeast    
Summary of Investment Holdings [Line Items]    
Fair Value 126,366 100,772
Healthcare, Education, and Childcare    
Summary of Investment Holdings [Line Items]    
Fair Value 245,796 273,262
Diversified/Conglomerate Manufacturing    
Summary of Investment Holdings [Line Items]    
Fair Value 220,479 202,466
Diversified/Conglomerate Service    
Summary of Investment Holdings [Line Items]    
Fair Value 147,229 152,042
Beverage, Food, and Tobacco    
Summary of Investment Holdings [Line Items]    
Fair Value 89,760 54,605
Cargo Transportation    
Summary of Investment Holdings [Line Items]    
Fair Value 49,928 20,000
Home and Office Furnishings, Housewares and Durable Consumer Products    
Summary of Investment Holdings [Line Items]    
Fair Value 29,882 30,000
Machinery    
Summary of Investment Holdings [Line Items]    
Fair Value 26,129 26,381
Personal, Food, and Miscellaneous Supplies    
Summary of Investment Holdings [Line Items]    
Fair Value 22,791 23,700
Ecological    
Summary of Investment Holdings [Line Items]    
Fair Value 18,000 0
Oil and Gas    
Summary of Investment Holdings [Line Items]    
Fair Value 15,998 17,512
Personal and Non-Durable Consumer Products    
Summary of Investment Holdings [Line Items]    
Fair Value 14,486 13,866
Automobile    
Summary of Investment Holdings [Line Items]    
Fair Value 9,337 27,361
Printing and Publishing    
Summary of Investment Holdings [Line Items]    
Fair Value 5,161 5,809
Other    
Summary of Investment Holdings [Line Items]    
Fair Value $ 11,868 $ 12,120
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 | Healthcare, Education, and Childcare    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 27.10% 31.80%
Investment Owned, At Fair Value | Industry Concentration Risk | Diversified/Conglomerate Manufacturing    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 24.30% 23.60%
Investment Owned, At Fair Value | Industry Concentration Risk | Diversified/Conglomerate Service    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 16.20% 17.70%
Investment Owned, At Fair Value | Industry Concentration Risk | Beverage, Food, and Tobacco    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 9.90% 6.40%
Investment Owned, At Fair Value | Industry Concentration Risk | Cargo Transportation    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 5.50% 2.30%
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 3.30% 3.50%
Investment Owned, At Fair Value | Industry Concentration Risk | Machinery    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 2.90% 3.10%
Investment Owned, At Fair Value | Industry Concentration Risk | Personal, Food, and Miscellaneous Supplies    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 2.50% 2.70%
Investment Owned, At Fair Value | Industry Concentration Risk | Ecological    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 2.00% 0.00%
Investment Owned, At Fair Value | Industry Concentration Risk | Oil and Gas    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 1.80% 2.00%
Investment Owned, At Fair Value | Industry Concentration Risk | Personal and Non-Durable Consumer Products    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 1.60% 1.60%
Investment Owned, At Fair Value | Industry Concentration Risk | Automobile    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 1.00% 3.20%
Investment Owned, At Fair Value | Industry Concentration Risk | Printing and Publishing    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 0.60% 0.70%
Investment Owned, At Fair Value | Industry Concentration Risk | Other    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 1.30% 1.40%
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 35.90% 33.50%
Investment Owned, At Fair Value | Geographic Regions Risk | West    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 25.70% 27.20%
Investment Owned, At Fair Value | Geographic Regions Risk | Midwest    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 24.40% 27.60%
Investment Owned, At Fair Value | Geographic Regions Risk | Northeast    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 14.00% 11.70%
Total debt investments    
Summary of Investment Holdings [Line Items]    
Cost $ 841,414 $ 796,623
Fair Value $ 816,009 $ 773,246
Total debt investments | Investment Owned, At Cost | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 90.90% 90.90%
Total debt investments | Investment Owned, At Fair Value | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 90.00% 90.00%
Secured first lien debt    
Summary of Investment Holdings [Line Items]    
Cost $ 655,732 $ 646,131
Fair Value $ 630,527 $ 622,371
Secured first lien debt | Investment Owned, At Cost | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 70.80% 73.70%
Secured first lien debt | Investment Owned, At Fair Value | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 69.50% 72.40%
Secured second lien debt    
Summary of Investment Holdings [Line Items]    
Cost $ 185,101 $ 149,937
Fair Value $ 185,141 $ 150,542
Secured second lien debt | Investment Owned, At Cost | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 20.00% 17.10%
Secured second lien debt | Investment Owned, At Fair Value | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 20.40% 17.50%
Unsecured debt    
Summary of Investment Holdings [Line Items]    
Cost $ 581 $ 555
Fair Value $ 341 $ 333
Unsecured debt | Investment Owned, At Cost | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 0.10% 0.10%
Unsecured debt | Investment Owned, At Fair Value | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 0.10% 0.10%
Total equity investments    
Summary of Investment Holdings [Line Items]    
Cost $ 83,779 $ 79,991
Fair Value $ 90,835 $ 85,878
Total equity investments | Investment Owned, At Cost | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 9.10% 9.10%
Total equity investments | Investment Owned, At Fair Value | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 10.00% 10.00%
Preferred Equity    
Summary of Investment Holdings [Line Items]    
Cost $ 42,369 $ 37,429
Fair Value $ 37,394 $ 31,214
Preferred Equity | Investment Owned, At Cost | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 4.60% 4.30%
Preferred Equity | Investment Owned, At Fair Value | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 4.10% 3.60%
Common Equity/ Equivalents    
Summary of Investment Holdings [Line Items]    
Cost $ 41,410 $ 42,562
Fair Value $ 53,441 $ 54,664
Common Equity/ Equivalents | Investment Owned, At Cost | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 4.50% 4.80%
Common Equity/ Equivalents | Investment Owned, At Fair Value | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 5.90% 6.40%
[1] Cumulative gross unrealized depreciation for federal income tax purposes is $59.7 million; cumulative gross unrealized appreciation for federal income tax purposes is $34.1 million. Cumulative net unrealized depreciation is $25.5 million, based on a tax cost of $884.7 million.