Quarterly report [Sections 13 or 15(d)]

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

v3.25.1
INVESTMENTS - Fair Value Measurement Inputs and Valuation Techniques (Details)
$ in Thousands
Mar. 31, 2025
USD ($)
Sep. 30, 2024
USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value $ 762,636 $ 796,260 [1]
Investments at fair value 762,636 796,260
Gladstone Alternative    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments at fair value 5,000  
Leeds Acquisition Holdings L L C    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value 36,000 38,000
Investments at fair value 36,000 38,000
Secured first lien debt    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments at fair value 541,524 554,937
Secured second lien debt    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments at fair value 144,970 113,716
Unsecured debt    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments at fair value 335 32
Significant Unobservable Inputs (Level 3)    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value 757,625 796,222
Investments at fair value 757,625 796,222
Significant Unobservable Inputs (Level 3) | Secured first lien debt    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments at fair value 541,524 554,937
Significant Unobservable Inputs (Level 3) | Secured second lien debt    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments at fair value 144,970 113,716
Significant Unobservable Inputs (Level 3) | Unsecured debt    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments at fair value 335 32
Significant Unobservable Inputs (Level 3) | Yield Analysis | Secured first lien debt    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value 467,857 464,090
Significant Unobservable Inputs (Level 3) | Yield Analysis | Secured second lien debt    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value $ 132,790 $ 101,928
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 0.099 0.108
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 0.175 0.173
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 0.117 0.126
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 0.117 0.122
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 0.154 0.160
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 0.133 0.141
Significant Unobservable Inputs (Level 3) | Market Quote | Secured second lien debt    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value $ 3,388 $ 3,241
Significant Unobservable Inputs (Level 3) | Market Quote | IBP | Secured second lien debt | Minimum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment owned, measurement input 0.920 0.880
Significant Unobservable Inputs (Level 3) | Market Quote | IBP | Secured second lien debt | Maximum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment owned, measurement input 0.920 0.880
Significant Unobservable Inputs (Level 3) | Market Quote | IBP | Secured second lien debt | Weighted Average    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment owned, measurement input 0.920 0.880
Significant Unobservable Inputs (Level 3) | TEV | Secured first lien debt    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value $ 73,667 $ 90,847
Significant Unobservable Inputs (Level 3) | TEV | Secured second lien debt    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value 8,792 8,547
Significant Unobservable Inputs (Level 3) | TEV | Unsecured debt    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value 335 32
Significant Unobservable Inputs (Level 3) | TEV | Preferred and common equity / equivalents    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value $ 70,796 $ 127,537
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 5.5 4.1
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 7.1 13.9
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 10
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 5.4 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 5.4 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 5.4 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 7.1 0
Significant Unobservable Inputs (Level 3) | TEV | EBITDA multiple | Unsecured debt | Maximum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment owned, measurement input 7.1 0
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 7.1 0
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 5 4.1
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 14.5 13.9
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 7.8 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 $ 2,504 $ 3,020
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 4,222 16,211
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 3,355 10,309
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 2,543 3,343
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 2,543 3,343
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 2,543 3,343
Significant Unobservable Inputs (Level 3) | TEV | EBITDA | Unsecured debt | Minimum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value 4,222 0
Significant Unobservable Inputs (Level 3) | TEV | EBITDA | Unsecured debt | Maximum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value 4,222 0
Significant Unobservable Inputs (Level 3) | TEV | EBITDA | Unsecured debt | Weighted Average    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value 4,222 0
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 1,318 1,182
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 144,799 144,458
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 $ 10,694 $ 10,847
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 0.4 0.2
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 0.7 4.6
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 0.6 2.1
Significant Unobservable Inputs (Level 3) | TEV | Revenue multiple | Unsecured debt | Minimum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment owned, measurement input 1 1
Significant Unobservable Inputs (Level 3) | TEV | Revenue multiple | Unsecured debt | Maximum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment owned, measurement input 1 1
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 1 1
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 0.4 0.2
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 1 4.6
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 0.5 2
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 $ 10,667 $ 6,336
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 21,318 21,118
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 15,691 13,981
Significant Unobservable Inputs (Level 3) | TEV | Revenue | Unsecured debt | Minimum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value 5,616 7,834
Significant Unobservable Inputs (Level 3) | TEV | Revenue | Unsecured debt | Maximum    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value 5,616 7,834
Significant Unobservable Inputs (Level 3) | TEV | Revenue | Unsecured debt | Weighted Average    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investments owned, fair value 5,616 7,834
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 5,402 4,672
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 21,318 21,118
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 $ 10,537 $ 12,587
[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.