Annual report pursuant to Section 13 and 15(d)

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)

v3.24.0.1
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)
$ in Millions
 12 Months Ended
Dec. 31, 2023
USD ($)
company
Dec. 31, 2022
USD ($)
company
Dec. 31, 2021
Schedule of Investments [Line Items]      
Cash equivalents | $ $ 20.8    
Cash balances exceeded Federal Deposit Insurance Corporation insurance protection levels | $ $ 9.0 $ 11.7  
Percentage of total investment income, attributable to noncash paid-in-kind interest income 3.80% 2.50% 2.30%
Percentage of total investment come, attributable to noncash cumulative dividend income 0.10% 0.60% 0.30%
Percentage of total investment income, attributable to interest income, debt investments, net 2.50% 2.50% 5.70%
Investment Owned, At Fair Value | Investment Type Concentration Risk      
Schedule of Investments [Line Items]      
Concentration risk, percentage 100.00% 100.00%  
Investment Owned, At Fair Value | Investment Type Concentration Risk | Nonperforming Financial Instruments      
Schedule of Investments [Line Items]      
Concentration risk, percentage 1.10% 0.80%  
Investment Owned, At Cost | Investment Type Concentration Risk      
Schedule of Investments [Line Items]      
Concentration risk, percentage 100.00% 100.00%  
Investment Owned, At Cost | Investment Type Concentration Risk | Nonperforming Financial Instruments      
Schedule of Investments [Line Items]      
Concentration risk, percentage 4.00% 4.80%  
Private Loan 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 55 51  
Percentage of portfolio with annual third-party appraisal was obtained, reviewed and certified 90.00% 94.00%  
Private Loan portfolio investments | Investment Owned, At Fair Value | Investment Type Concentration Risk      
Schedule of Investments [Line Items]      
Concentration risk, percentage 79.00% 83.00%  
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 46 44  
Percentage of portfolio with annual third-party appraisal was obtained, reviewed and certified 99.00% 99.00%  
LMM portfolio investments | Investment Owned, At Fair Value | Investment Type Concentration Risk      
Schedule of Investments [Line Items]      
Concentration risk, percentage 95.00% 97.00%  
Middle Market portfolio investments      
Schedule of Investments [Line Items]      
Percentage of portfolio investments containing limited consultation with financial advisory services firm 97.00% 91.00%  
Other Portfolio investments | Investment Owned, At Fair Value | Investment Type Concentration Risk      
Schedule of Investments [Line Items]      
Concentration risk, percentage 2.30% 2.70%  
Other Portfolio investments | Investment Owned, At Cost | Investment Type Concentration Risk      
Schedule of Investments [Line Items]      
Concentration risk, percentage 2.10% 2.30%