Quarterly report pursuant to Section 13 or 15(d)

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)

v3.23.3
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)
$ in Millions
 3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2023
USD ($)
company
Sep. 30, 2022
company
Sep. 30, 2023
USD ($)
Sep. 30, 2022
Sep. 30, 2023
USD ($)
company
Dec. 31, 2022
USD ($)
Schedule of Investments [Line Items]            
Cash equivalents | $ $ 19.6   $ 19.6   $ 19.6  
Cash balances exceeded Federal Deposit Insurance Corporation insurance protection levels | $ $ 3.2   $ 3.2   $ 3.2 $ 11.7
Percentage of total investment income, attributable to noncash paid-in-kind interest income 4.60% 2.30% 3.90% 2.50%    
Percentage of total investment come, attributable to noncash cumulative dividend income 0.10% 0.40% 0.10% 0.80%    
Percentage of total investment income, attributable to interest income, debt investments, net 2.60% 2.30% 2.60% 2.60%    
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     1.70%     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     5.20%     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 14 13     56  
Percentage of portfolio with annual third-party appraisal was obtained, reviewed and certified         91.00%  
Private Loan portfolio investments | Investment Owned, At Fair Value | Investment Type Concentration Risk            
Schedule of Investments [Line Items]            
Concentration risk, percentage     21.00% 18.00% 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 12 11     46  
Percentage of portfolio with annual third-party appraisal was obtained, reviewed and certified         100.00%  
LMM portfolio investments | Investment Owned, At Fair Value | Investment Type Concentration Risk            
Schedule of Investments [Line Items]            
Concentration risk, percentage     25.00% 25.00% 95.00%  
Middle Market portfolio investments            
Schedule of Investments [Line Items]            
Percentage of portfolio investments containing limited consultation with financial advisory services firm 93.00%   93.00%   93.00% 91.00%
Other Portfolio investments | Investment Owned, At Fair Value | Investment Type Concentration Risk            
Schedule of Investments [Line Items]            
Concentration risk, percentage     2.40%     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%