Quarterly report pursuant to Section 13 or 15(d)

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)

v3.24.1.1.u2
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)
$ in Millions
 3 Months Ended 12 Months Ended
Mar. 31, 2024
USD ($)
company
Mar. 31, 2023
company
Mar. 31, 2024
USD ($)
company
Dec. 31, 2023
USD ($)
Schedule of Investments [Line Items]        
Cash equivalents | $ $ 13.6   $ 13.6 $ 20.8
Cash balances exceeded federal deposit insurance corporation insurance protection levels | $ $ 10.8   $ 10.8 $ 9.0
Percentage of total investment income, attributable to noncash paid-in-kind interest income (as a percent) 4.50% 3.80%    
Percentage of total investment income, attributable to noncash cumulative dividend income (as a percent) 0.10% 0.10%    
Percentage of total investment income, attributable to interest income, debt investments, net (as a percent) 2.50% 2.50%    
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) 0.70%     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) 3.60%     4.00%
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 14 55  
Percentage of portfolio with annual third-party appraisal was obtained, reviewed and certified (as a percent)     91.00%  
Private Loan portfolio investments | Investment Owned, At Fair Value | Investment Type Concentration Risk        
Schedule of Investments [Line Items]        
Concentration risk, percentage (as a percent) 21.00% 24.00% 78.00%  
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 13 46  
Percentage of portfolio with annual third-party appraisal was obtained, reviewed and certified (as a percent)     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) 26.00% 39.00% 94.00%  
Middle Market portfolio investments        
Schedule of Investments [Line Items]        
Percentage of portfolio investments containing limited consultation with financial advisory services firm (as a percent) 96.00%   96.00% 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) 2.20%     2.30%
Other Portfolio investments | Investment Owned, At Cost | Investment Type Concentration Risk        
Schedule of Investments [Line Items]        
Concentration risk, percentage (as a percent) 2.00%     2.10%