Quarterly report [Sections 13 or 15(d)]

INVESTMENTS - Summary Investment Holdings (Details)

v3.25.1
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.