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
 9 Months Ended 12 Months Ended
Jun. 30, 2026
Sep. 30, 2025
Summary of Investment Holdings [Line Items]    
Cost $ 968,661 $ 876,614 [1]
Fair Value 953,326 859,124 [1]
South    
Summary of Investment Holdings [Line Items]    
Fair Value 373,171 287,371
Midwest    
Summary of Investment Holdings [Line Items]    
Fair Value 231,723 237,417
West    
Summary of Investment Holdings [Line Items]    
Fair Value 198,233 233,564
Northeast    
Summary of Investment Holdings [Line Items]    
Fair Value 150,199 100,772
Diversified/Conglomerate Manufacturing    
Summary of Investment Holdings [Line Items]    
Fair Value 289,704 202,466
Healthcare, Education, and Childcare    
Summary of Investment Holdings [Line Items]    
Fair Value 220,268 273,262
Diversified/Conglomerate Service    
Summary of Investment Holdings [Line Items]    
Fair Value 151,376 152,042
Beverage, Food, and Tobacco    
Summary of Investment Holdings [Line Items]    
Fair Value 86,132 54,605
Cargo Transportation    
Summary of Investment Holdings [Line Items]    
Fair Value 50,000 20,000
Home and Office Furnishings, Housewares and Durable Consumer Products    
Summary of Investment Holdings [Line Items]    
Fair Value 34,793 30,000
Machinery    
Summary of Investment Holdings [Line Items]    
Fair Value 25,768 26,381
Personal, Food, and Miscellaneous Services    
Summary of Investment Holdings [Line Items]    
Fair Value 22,493 23,700
Ecological    
Summary of Investment Holdings [Line Items]    
Fair Value 18,201 0
Personal and Non-Durable Consumer Products    
Summary of Investment Holdings [Line Items]    
Fair Value 16,246 13,866
Oil and Gas    
Summary of Investment Holdings [Line Items]    
Fair Value 13,510 17,512
Automobile    
Summary of Investment Holdings [Line Items]    
Fair Value 8,099 27,361
Printing and Publishing    
Summary of Investment Holdings [Line Items]    
Fair Value 4,385 5,809
Other    
Summary of Investment Holdings [Line Items]    
Fair Value $ 12,351 $ 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 | Diversified/Conglomerate Manufacturing    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 30.40% 23.60%
Investment Owned, At Fair Value | Industry Concentration Risk | Healthcare, Education, and Childcare    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 23.10% 31.80%
Investment Owned, At Fair Value | Industry Concentration Risk | Diversified/Conglomerate Service    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 15.90% 17.70%
Investment Owned, At Fair Value | Industry Concentration Risk | Beverage, Food, and Tobacco    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 9.00% 6.40%
Investment Owned, At Fair Value | Industry Concentration Risk | Cargo Transportation    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 5.20% 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 3.60% 3.50%
Investment Owned, At Fair Value | Industry Concentration Risk | Machinery    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 2.70% 3.10%
Investment Owned, At Fair Value | Industry Concentration Risk | Personal, Food, and Miscellaneous Services    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 2.40% 2.70%
Investment Owned, At Fair Value | Industry Concentration Risk | Ecological    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 1.90% 0.00%
Investment Owned, At Fair Value | Industry Concentration Risk | Personal and Non-Durable Consumer Products    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 1.70% 1.60%
Investment Owned, At Fair Value | Industry Concentration Risk | Oil and Gas    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 1.40% 2.00%
Investment Owned, At Fair Value | Industry Concentration Risk | Automobile    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 0.90% 3.20%
Investment Owned, At Fair Value | Industry Concentration Risk | Printing and Publishing    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 0.50% 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 39.10% 33.50%
Investment Owned, At Fair Value | Geographic Regions Risk | Midwest    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 24.30% 27.60%
Investment Owned, At Fair Value | Geographic Regions Risk | West    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 20.80% 27.20%
Investment Owned, At Fair Value | Geographic Regions Risk | Northeast    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 15.80% 11.70%
Total debt investments    
Summary of Investment Holdings [Line Items]    
Cost $ 877,169 $ 796,623
Fair Value $ 852,034 $ 773,246
Total debt investments | Investment Owned, At Cost | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 90.60% 90.90%
Total debt investments | Investment Owned, At Fair Value | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 89.40% 90.00%
Secured first lien debt    
Summary of Investment Holdings [Line Items]    
Cost $ 690,585 $ 646,131
Fair Value $ 665,834 $ 622,371
Secured first lien debt | Investment Owned, At Cost | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 71.30% 73.70%
Secured first lien debt | Investment Owned, At Fair Value | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 69.80% 72.40%
Secured second lien debt    
Summary of Investment Holdings [Line Items]    
Cost $ 185,990 $ 149,937
Fair Value $ 185,844 $ 150,542
Secured second lien debt | Investment Owned, At Cost | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 19.20% 17.10%
Secured second lien debt | Investment Owned, At Fair Value | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 19.50% 17.50%
Unsecured debt    
Summary of Investment Holdings [Line Items]    
Cost $ 594 $ 555
Fair Value $ 356 $ 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 $ 91,492 $ 79,991
Fair Value $ 101,292 $ 85,878
Total equity investments | Investment Owned, At Cost | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 9.40% 9.10%
Total equity investments | Investment Owned, At Fair Value | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 10.60% 10.00%
Preferred Equity    
Summary of Investment Holdings [Line Items]    
Cost $ 44,369 $ 37,429
Fair Value $ 40,876 $ 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 4.30% 3.60%
Common Equity/ Equivalents    
Summary of Investment Holdings [Line Items]    
Cost $ 47,123 $ 42,562
Fair Value $ 60,416 $ 54,664
Common Equity/ Equivalents | Investment Owned, At Cost | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 4.80% 4.80%
Common Equity/ Equivalents | Investment Owned, At Fair Value | Investment Type Concentration Risk    
Summary of Investment Holdings [Line Items]    
Concentration Risk, Percentage 6.30% 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.