Quarterly report [Sections 13 or 15(d)]

RELATED PARTY TRANSACTIONS - Narrative (Details)

v3.26.1
RELATED PARTY TRANSACTIONS - Narrative (Details) - USD ($)
3 Months Ended 12 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Mar. 31, 2026
Related Party Transaction [Line Items]      
Base management fee (as a percent) 2.00% 2.00%  
Base management fee, percent fee 100.00%    
Investment company, excess expense reimbursable $ 100,000 $ 100,000  
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 7.18% 4.07%  
Investment company, capital gains-based incentive fees $ 0   $ 0
Investment company, capital gains-based incentive fees reversal 5,600,000 $ 200,000  
Accrued capital gains-based incentive fee 71,700,000   77,300,000
Administration fee [1] 492,000 433,000  
Success fee income 5,591,000 754,000  
Related Party      
Related Party Transaction [Line Items]      
Success fee income 0 $ 600,000  
Due from related parties 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%    
Affiliated Entity | Minimum | Advisory Agreement      
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%    
Administrator | Chief Executive Officer | Related Party      
Related Party Transaction [Line Items]      
Ownership percentage by parent 100.00%    
Gladstone Securities, LLC | Chief Executive Officer | Related Party      
Related Party Transaction [Line Items]      
Ownership percentage by parent 100.00%    
[1] Refer to Note 4 — Related Party Transactions in the accompanying Notes to Consolidated Financial Statements for additional information.