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

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)

v3.25.1
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)
$ in Millions
 12 Months Ended
Dec. 31, 2024
USD ($)
company
segment
Dec. 31, 2023
USD ($)
company
Dec. 31, 2022
Schedule of Investments [Line Items]      
Concentration risk, percentage (as a percent) 100.00% 100.00%  
Cash equivalents | $ $ 14.4 $ 20.8  
Cash balances exceeded federal deposit insurance corporation insurance protection levels | $ $ 13.5 $ 9.0  
Percentage of total investment income, attributable to noncash paid-in-kind interest income (as a percent) 6.20% 3.80% 2.50%
Percentage of total investment income, attributable to noncash cumulative dividend income (as a percent) 0.10% 0.10% 0.60%
Percentage of total investment income, attributable to interest income, debt investments, net (as a percent) 2.80% 2.50% 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) 1.50% 1.10%  
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) 5.60% 4.00%  
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 63 55  
Percentage of portfolio with annual third-party appraisal was obtained, reviewed and certified (as a percent) 96.00% 90.00%  
Private Loan | Investment Owned, At Fair Value | Investment Type Concentration Risk      
Schedule of Investments [Line Items]      
Concentration risk, percentage (as a percent) 85.00% 79.00%  
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 48 46  
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) 92.00% 95.00%  
Middle Market      
Schedule of Investments [Line Items]      
Percentage of portfolio investments containing limited consultation with financial advisory services firm (as a percent) 93.00% 97.00%  
Other Portfolio investments | Investment Owned, At Fair Value | Investment Type Concentration Risk      
Schedule of Investments [Line Items]      
Concentration risk, percentage (as a percent) 2.00% 2.30%  
Other Portfolio investments | Investment Owned, At Cost | Investment Type Concentration Risk      
Schedule of Investments [Line Items]      
Concentration risk, percentage (as a percent) 1.60% 2.10%