Quarterly report pursuant to Section 13 or 15(d)

RELATED PARTY TRANSACTIONS - Narrative (Details)

v3.25.0.1
RELATED PARTY TRANSACTIONS - Narrative (Details) - USD ($)
 3 Months Ended 9 Months Ended 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2024
Dec. 31, 2023
Mar. 31, 2024
Related Party Transaction [Line Items]          
Base management fee (as a percent) 2.00% 2.00% 2.00% 2.00%  
Base management fee, percent fee     100.00%    
Investment company, excess expense reimbursable $ 163,000 $ 57,000 $ 315,000 $ 215,000  
Maximum base management fee paid cannot exceed a percentage of total assets     2.00%    
Ratio of net investment income (loss) to average net assets – annualized (3.56%) 4.73% 4.18% 1.32%  
Investment company, capital gains-based incentive fees     $ 4,900,000   $ 1,100,000
Investment company, capital gains-based incentive fees payable (reversal) $ 7,500,000 $ (600,000) 5,300,000 $ 9,300,000  
Accrued capital gains-based incentive fee 42,100,000   42,100,000   36,700,000
Administration fee [1] 405,000 450,000 1,478,000 1,306,000  
Success fee income 843,000 1,382,000 2,546,000 1,382,000  
Related Party          
Related Party Transaction [Line Items]          
Success fee income 1,700,000 $ 0 1,900,000 $ 300,000  
Due from related parties $ 100,000   100,000   $ 100,000
Affiliated Entity | Advisory Agreement          
Related Party Transaction [Line Items]          
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]          
Ownership percentage by parent 100.00%   100.00%    
Administrator | Chief Executive Officer | Related Party          
Related Party Transaction [Line Items]          
Ownership percentage by parent 100.00%   100.00%    
Gladstone Securities, LLC | Chief Executive Officer | Related Party          
Related Party Transaction [Line Items]          
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.