Annual report [Section 13 and 15(d), not S-K Item 405]

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)

v3.25.4
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)
$ in Millions
 12 Months Ended
Dec. 31, 2025
USD ($)
segment
company
Dec. 31, 2024
USD ($)
company
Dec. 31, 2023
Schedule of Investments [Line Items]      
Concentration risk, percentage (as a percent) 100.00% 100.00%  
Cash equivalents | $ $ 11.1 $ 14.4  
Cash balances exceeded federal deposit insurance corporation insurance protection levels | $ $ 8.5 $ 13.5  
Percentage of total investment income, attributable to noncash paid-in-kind interest income (as a percent) 6.00% 6.20% 3.80%
Percentage of total investment income, attributable to noncash cumulative dividend income (as a percent) 0.90% 0.10% 0.10%
Percentage of total investment income, attributable to interest income, debt investments, net (as a percent) 2.40% 2.80% 2.50%
Number of reportable segments | segment 1    
Number of operating segments | segment 1    
Investment Owned, At Fair Value | Investment Type Concentration Risk      
Schedule of Investments [Line Items]      
Concentration risk, percentage (as a percent) 100.00% 100.00%  
Investment Owned, At Fair Value | Investment Type Concentration Risk | Nonperforming Financial Instruments      
Schedule of Investments [Line Items]      
Concentration risk, percentage (as a percent) 1.00% 1.50%  
Investment Owned, At Cost | Investment Type Concentration Risk      
Schedule of Investments [Line Items]      
Concentration risk, percentage (as a percent) 100.00% 100.00%  
Investment Owned, At Cost | Investment Type Concentration Risk | Nonperforming Financial Instruments      
Schedule of Investments [Line Items]      
Concentration risk, percentage (as a percent) 3.90% 5.60%  
Private Loan      
Schedule of Investments [Line Items]      
Consultation period subsequent to initial investment 12 months    
Investment company, number of portfolio companies with annual third-party appraisal was obtained, reviewed and certified | company 59 63  
Percentage of portfolio with annual third-party appraisal was obtained, reviewed and certified (as a percent) 97.00% 96.00%  
Private Loan | Investment Owned, At Fair Value | Investment Type Concentration Risk      
Schedule of Investments [Line Items]      
Concentration risk, percentage (as a percent) 81.00% 85.00%  
LMM portfolio investments      
Schedule of Investments [Line Items]      
Consultation period subsequent to initial investment 12 months    
Investment company, number of portfolio companies with annual third-party appraisal was obtained, reviewed and certified | company 49 48  
Percentage of portfolio with annual third-party appraisal was obtained, reviewed and certified (as a percent) 99.00% 99.00%  
LMM portfolio investments | Investment Owned, At Fair Value | Investment Type Concentration Risk      
Schedule of Investments [Line Items]      
Concentration risk, percentage (as a percent) 96.00% 92.00%  
Middle Market      
Schedule of Investments [Line Items]      
Percentage of portfolio investments containing limited consultation with financial advisory services firm (as a percent) 85.00% 93.00%  
Middle Market | Investment Owned, At Fair Value | Investment Type Concentration Risk      
Schedule of Investments [Line Items]      
Concentration risk, percentage (as a percent) 1.70% 3.30%  
Middle Market | Investment Owned, At Cost | Investment Type Concentration Risk      
Schedule of Investments [Line Items]      
Concentration risk, percentage (as a percent) 3.20% 5.80%  
Other Portfolio investments | Investment Owned, At Fair Value | Investment Type Concentration Risk      
Schedule of Investments [Line Items]      
Concentration risk, percentage (as a percent) 1.20% 2.00%  
Other Portfolio investments | Investment Owned, At Cost | Investment Type Concentration Risk      
Schedule of Investments [Line Items]      
Concentration risk, percentage (as a percent) 1.10% 1.60%