Quarterly report pursuant to Section 13 or 15(d)

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)

v3.23.2
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)
$ in Millions
 3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2023
USD ($)
company
investment
Jun. 30, 2022
company
Jun. 30, 2023
USD ($)
company
investment
Jun. 30, 2022
company
Dec. 31, 2022
USD ($)
investment
Schedule of Investments [Line Items]          
Cash exceeded federal deposit insurance corporation insurance protection levels | $ $ 46.0   $ 46.0   $ 46.3
Percentage of total investment income, attributable to noncash paid-in-kind interest income 1.80% 1.70% 2.10% 1.40%  
Percentage of total investment come, attributable to noncash cumulative dividend income 0.20% 0.20% 0.30% 0.60%  
Percentage of total investment income, attributable to interest income, debt investments, net 1.80% 2.00% 1.80% 2.00%  
Investment Owned, At Fair Value | Investment Type Concentration Risk          
Schedule of Investments [Line Items]          
Concentration risk, percentage     100.00%   100.00%
Investment Owned, At Cost | Investment Type Concentration Risk          
Schedule of Investments [Line Items]          
Concentration risk, percentage     100.00%   100.00%
Non-accrual Status          
Schedule of Investments [Line Items]          
Number of investments | investment 9   9   12
Non-accrual Status | Investment Owned, At Fair Value | Investment Type Concentration Risk          
Schedule of Investments [Line Items]          
Concentration risk, percentage     0.30%   0.60%
Non-accrual Status | Investment Owned, At Cost | Investment Type Concentration Risk          
Schedule of Investments [Line Items]          
Concentration risk, percentage     1.70%   3.70%
Revolving Credit Facility | Line of Credit          
Schedule of Investments [Line Items]          
Commitment fee (in percentage)     3.40%    
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 37 36 37 36  
Percentage of portfolio with annual third-party appraisal was obtained, reviewed and certified     55.00% 61.00%  
LMM portfolio investments | Investment Owned, At Fair Value | Investment Type Concentration Risk          
Schedule of Investments [Line Items]          
Concentration risk, percentage     52.00% 54.00%  
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 33 29 33 29  
Percentage of portfolio with annual third-party appraisal was obtained, reviewed and certified     53.00% 67.00%  
Private Loan portfolio investments | Investment Owned, At Fair Value | Investment Type Concentration Risk          
Schedule of Investments [Line Items]          
Concentration risk, percentage     49.00% 44.00%  
Middle Market portfolio investments          
Schedule of Investments [Line Items]          
Percentage of portfolio investments containing limited consultation with financial advisory services firm 90.00%   90.00%   89.00%
Other Portfolio investments | Investment Owned, At Fair Value | Investment Type Concentration Risk          
Schedule of Investments [Line Items]          
Concentration risk, percentage     2.60%   2.80%
Other Portfolio investments | Investment Owned, At Cost | Investment Type Concentration Risk          
Schedule of Investments [Line Items]          
Concentration risk, percentage     3.20%   3.20%