Quarterly report [Sections 13 or 15(d)]

INVESTMENTS - Schedule of Fair Value Measurement Inputs and Valuation Techniques (Details)

v3.25.4
INVESTMENTS - Schedule of Fair Value Measurement Inputs and Valuation Techniques (Details)
$ in Thousands
Dec. 31, 2025
USD ($)
investment
Sep. 30, 2025
USD ($)
investment
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value $ 902,912 $ 859,124 [1]
Investments at fair value 902,912 859,124
Gladstone Alternative    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments at fair value 5,100 5,100
Leeds Acquisition Holdings L L C    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments at fair value   36,000
Secured first lien debt    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments at fair value 647,576 622,371
Secured second lien debt    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments at fair value 170,662 150,542
Unsecured debt    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments at fair value 346 333
Significant Unobservable Inputs (Level 3)    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value 897,837 854,013
Investments at fair value 897,837 854,013
Significant Unobservable Inputs (Level 3) | Secured first lien debt    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments at fair value 647,576 622,371
Significant Unobservable Inputs (Level 3) | Secured second lien debt    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments at fair value 170,662 150,542
Significant Unobservable Inputs (Level 3) | Unsecured debt    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments at fair value 346 333
Significant Unobservable Inputs (Level 3) | Measurement Input, Expected Payoff Amount | Preferred and common equity / equivalents    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value $ 43,600 $ 2,200
Investment owned, number of investments | investment 1 1
Significant Unobservable Inputs (Level 3) | Yield Analysis | Secured first lien debt    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value $ 570,154 $ 548,670
Significant Unobservable Inputs (Level 3) | Yield Analysis | Secured second lien debt    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value $ 151,870 $ 141,750
Significant Unobservable Inputs (Level 3) | Yield Analysis | Discount Rate | Secured first lien debt | Minimum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment owned, measurement input 0.090 0.094
Significant Unobservable Inputs (Level 3) | Yield Analysis | Discount Rate | Secured first lien debt | Maximum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment owned, measurement input 0.180 0.198
Significant Unobservable Inputs (Level 3) | Yield Analysis | Discount Rate | Secured first lien debt | Weighted Average    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment owned, measurement input 0.112 0.117
Significant Unobservable Inputs (Level 3) | Yield Analysis | Discount Rate | Secured second lien debt | Minimum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment owned, measurement input 0.111 0.114
Significant Unobservable Inputs (Level 3) | Yield Analysis | Discount Rate | Secured second lien debt | Maximum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment owned, measurement input 0.148 0.152
Significant Unobservable Inputs (Level 3) | Yield Analysis | Discount Rate | Secured second lien debt | Weighted Average    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment owned, measurement input 0.123 0.131
Significant Unobservable Inputs (Level 3) | TEV | Secured first lien debt    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value $ 77,422 $ 73,701
Significant Unobservable Inputs (Level 3) | TEV | Secured second lien debt    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value 18,792 8,792
Significant Unobservable Inputs (Level 3) | TEV | Unsecured debt    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value 346 333
Significant Unobservable Inputs (Level 3) | TEV | Preferred and common equity / equivalents    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value $ 79,253 $ 80,767
Significant Unobservable Inputs (Level 3) | TEV | EBITDA multiple | Secured first lien debt | Minimum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment owned, measurement input 3.6 3.5
Significant Unobservable Inputs (Level 3) | TEV | EBITDA multiple | Secured first lien debt | Maximum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment owned, measurement input 8.3 8
Significant Unobservable Inputs (Level 3) | TEV | EBITDA multiple | Secured first lien debt | Weighted Average    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment owned, measurement input 6.2 6
Significant Unobservable Inputs (Level 3) | TEV | EBITDA multiple | Secured second lien debt | Minimum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment owned, measurement input 5 5.4
Significant Unobservable Inputs (Level 3) | TEV | EBITDA multiple | Secured second lien debt | Maximum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment owned, measurement input 5.6 5.4
Significant Unobservable Inputs (Level 3) | TEV | EBITDA multiple | Secured second lien debt | Weighted Average    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment owned, measurement input 5.3 5.4
Significant Unobservable Inputs (Level 3) | TEV | EBITDA multiple | Unsecured debt | Minimum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment owned, measurement input 8.3 8
Significant Unobservable Inputs (Level 3) | TEV | EBITDA multiple | Unsecured debt | Maximum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment owned, measurement input 8.3 8
Significant Unobservable Inputs (Level 3) | TEV | EBITDA multiple | Unsecured debt | Weighted Average    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment owned, measurement input 8.3 8
Significant Unobservable Inputs (Level 3) | TEV | EBITDA multiple | Preferred and common equity / equivalents | Minimum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment owned, measurement input 3.6 3.5
Significant Unobservable Inputs (Level 3) | TEV | EBITDA multiple | Preferred and common equity / equivalents | Maximum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment owned, measurement input 15.1 14.6
Significant Unobservable Inputs (Level 3) | TEV | EBITDA multiple | Preferred and common equity / equivalents | Weighted Average    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment owned, measurement input 7 6.8
Significant Unobservable Inputs (Level 3) | TEV | EBITDA | Secured first lien debt | Minimum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value $ 490 $ 538
Significant Unobservable Inputs (Level 3) | TEV | EBITDA | Secured first lien debt | Maximum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value 4,266 4,655
Significant Unobservable Inputs (Level 3) | TEV | EBITDA | Secured first lien debt | Weighted Average    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value 3,485 3,540
Significant Unobservable Inputs (Level 3) | TEV | EBITDA | Secured second lien debt | Minimum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value 2,355 2,345
Significant Unobservable Inputs (Level 3) | TEV | EBITDA | Secured second lien debt | Maximum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value 11,359 2,345
Significant Unobservable Inputs (Level 3) | TEV | EBITDA | Secured second lien debt | Weighted Average    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value 7,146 2,345
Significant Unobservable Inputs (Level 3) | TEV | EBITDA | Unsecured debt | Minimum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value 3,755 3,804
Significant Unobservable Inputs (Level 3) | TEV | EBITDA | Unsecured debt | Maximum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value 3,755 3,804
Significant Unobservable Inputs (Level 3) | TEV | EBITDA | Unsecured debt | Weighted Average    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value 3,755 3,804
Significant Unobservable Inputs (Level 3) | TEV | EBITDA | Preferred and common equity / equivalents | Minimum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value 490 538
Significant Unobservable Inputs (Level 3) | TEV | EBITDA | Preferred and common equity / equivalents | Maximum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value 143,118 142,549
Significant Unobservable Inputs (Level 3) | TEV | EBITDA | Preferred and common equity / equivalents | Weighted Average    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value $ 9,727 $ 10,222
Significant Unobservable Inputs (Level 3) | TEV | Revenue multiple | Secured first lien debt | Minimum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment owned, measurement input 0.6 0.6
Significant Unobservable Inputs (Level 3) | TEV | Revenue multiple | Secured first lien debt | Maximum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment owned, measurement input 0.8 0.8
Significant Unobservable Inputs (Level 3) | TEV | Revenue multiple | Secured first lien debt | Weighted Average    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment owned, measurement input 0.7 0.7
Significant Unobservable Inputs (Level 3) | TEV | Revenue multiple | Unsecured debt | Minimum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment owned, measurement input 0.9 0.9
Significant Unobservable Inputs (Level 3) | TEV | Revenue multiple | Unsecured debt | Maximum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment owned, measurement input 0.9 0.9
Significant Unobservable Inputs (Level 3) | TEV | Revenue multiple | Unsecured debt | Weighted Average    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment owned, measurement input 0.9 0.9
Significant Unobservable Inputs (Level 3) | TEV | Revenue multiple | Preferred and common equity / equivalents | Minimum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment owned, measurement input 0.6 0.6
Significant Unobservable Inputs (Level 3) | TEV | Revenue multiple | Preferred and common equity / equivalents | Maximum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment owned, measurement input 0.9 0.9
Significant Unobservable Inputs (Level 3) | TEV | Revenue multiple | Preferred and common equity / equivalents | Weighted Average    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment owned, measurement input 0.7 0.7
Significant Unobservable Inputs (Level 3) | TEV | Revenue | Secured first lien debt | Minimum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value $ 8,268 $ 10,844
Significant Unobservable Inputs (Level 3) | TEV | Revenue | Secured first lien debt | Maximum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value 22,244 21,649
Significant Unobservable Inputs (Level 3) | TEV | Revenue | Secured first lien debt | Weighted Average    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value 14,884 15,090
Significant Unobservable Inputs (Level 3) | TEV | Revenue | Unsecured debt | Minimum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value 4,708 4,846
Significant Unobservable Inputs (Level 3) | TEV | Revenue | Unsecured debt | Maximum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value 4,708 4,846
Significant Unobservable Inputs (Level 3) | TEV | Revenue | Unsecured debt | Weighted Average    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value 4,708 4,846
Significant Unobservable Inputs (Level 3) | TEV | Revenue | Preferred and common equity / equivalents | Minimum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value 4,708 4,846
Significant Unobservable Inputs (Level 3) | TEV | Revenue | Preferred and common equity / equivalents | Maximum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value 22,244 21,649
Significant Unobservable Inputs (Level 3) | TEV | Revenue | Preferred and common equity / equivalents | Weighted Average    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value $ 11,209 $ 12,394
[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.