Quarterly report pursuant to Section 13 or 15(d)

RELATED PARTY TRANSACTIONS - Narrative (Details)

v3.23.3
RELATED PARTY TRANSACTIONS - Narrative (Details) - USD ($)
3 Months Ended 6 Months Ended 12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2023
Sep. 30, 2022
Mar. 31, 2023
Related Party Transaction [Line Items]          
Base management fee 2.00% 2.00% 2.00% 2.00%  
Investment company, excess expense reimbursable $ 83,000 $ 70,000 $ 158,000 $ 106,000  
Ratio of net investment income (loss) to average net assets – annualized (5.39%) 7.01% (0.50%) 5.69%  
Investment company, capital gains-based incentive fees     $ 0   $ 0
Investment company, capital gains-based incentive fees payable (reversal) $ 9,800,000 $ (1,700,000) 9,900,000 $ (700,000)  
Administration fee [1] 334,000 562,000 856,000 942,000  
Success fee income 0 1,733,000 0 6,733,000  
Related Party          
Related Party Transaction [Line Items]          
Success fee income   $ 1,000,000 300,000 $ 1,300,000  
Due from related parties $ 19,000   $ 19,000   $ 0
Affiliated Entity | Advisory Agreement          
Related Party Transaction [Line Items]          
Base management fee     2.00%    
Base management fee, percent fee     100.00%    
Maximum base management fee paid cannot exceed a percentage of total assets     2.00%    
Incentive fee base on minimum rate of return required on investment     $ 0    
Percentage of pre-incentive fee net investment income is less than the hurdle rate     100.00%    
Investment company, pre-incentive fee net investment income, percent threshold of net assets     2.1875%    
Pre-incentive fee net investment income exceeds the hurdle rate     20.00%    
Investment company, capital gains-based incentive fees 20.00%   20.00%    
Affiliated Entity | Advisory Agreement | Minimum          
Related Party Transaction [Line Items]          
Ratio of net investment income (loss) to average net assets – annualized     1.75%    
Adviser | Chief Executive Officer | Related Party          
Related Party Transaction [Line Items]          
Noncontrolling interest, ownership percentage by parent 100.00%   100.00%    
Administrator | Chief Executive Officer | Related Party          
Related Party Transaction [Line Items]          
Noncontrolling interest, ownership percentage by parent 100.00%   100.00%    
Gladstone Securities, LLC | Chief Executive Officer | Related Party          
Related Party Transaction [Line Items]          
Noncontrolling interest, ownership percentage by parent 100.00%   100.00%    
[1] Refer to Note 4 — Related Party Transactions in the accompanying Notes to Consolidated Financial Statements for additional information.