Quarterly report pursuant to Section 13 or 15(d)

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)

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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)
$ in Millions
 3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2024
USD ($)
company
Jun. 30, 2023
company
Jun. 30, 2024
USD ($)
Jun. 30, 2023
Jun. 30, 2024
USD ($)
company
Dec. 31, 2023
USD ($)
Schedule of Investments [Line Items]            
Cash equivalents | $ $ 15.0   $ 15.0   $ 15.0 $ 20.8
Cash balances exceeded federal deposit insurance corporation insurance protection levels | $ $ 13.1   $ 13.1   $ 13.1 $ 9.0
Percentage of total investment income, attributable to noncash paid-in-kind interest income (as a percent) 5.00% 3.40% 4.70% 3.60%    
Percentage of total investment income, attributable to noncash cumulative dividend income (as a percent) 0.10% 0.10% 0.10% 0.10%    
Percentage of total investment income, attributable to interest income, debt investments, net (as a percent) 2.80% 2.60% 2.70% 2.60%    
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 | Nonperforming Financial Instruments | Investment Type Concentration Risk            
Schedule of Investments [Line Items]            
Concentration risk, percentage (as a percent)     1.80%     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 | Nonperforming Financial Instruments | Investment Type Concentration Risk            
Schedule of Investments [Line Items]            
Concentration risk, percentage (as a percent)     5.30%     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 18 13     57  
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) 22.00% 15.00%     76.00%  
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 14 12     48  
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) 27.00% 19.00%     93.00%  
Middle Market portfolio investments            
Schedule of Investments [Line Items]            
Percentage of portfolio investments containing limited consultation with financial advisory services firm (as a percent) 94.00%   94.00%   94.00% 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)     2.30%     2.30%
Other Portfolio investments | Investment Owned, At Cost | Investment Type Concentration Risk            
Schedule of Investments [Line Items]            
Concentration risk, percentage (as a percent)     1.80%     2.10%