Quarterly report [Sections 13 or 15(d)]

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)

v3.25.3
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)
$ in Millions
 3 Months Ended 9 Months Ended 12 Months Ended 15 Months Ended
Sep. 30, 2025
USD ($)
company
Sep. 30, 2024
company
Sep. 30, 2025
USD ($)
segment
Sep. 30, 2024
Dec. 31, 2024
USD ($)
Sep. 30, 2025
USD ($)
company
Schedule of Investments [Line Items]            
Cash equivalents | $ $ 10.6   $ 10.6   $ 6.5 $ 10.6
Cash exceeded federal deposit insurance corporation insurance protection levels | $ $ 17.0   $ 17.0   $ 67.5 $ 17.0
Percentage of total investment income, attributable to noncash paid-in-kind interest income (as a percent) 3.00% 4.40% 2.70% 3.80%    
Percentage of total investment come, attributable to noncash cumulative dividend income (as a percent) 0.70% 0.50% 0.70% 0.40%    
Percentage of total investment income, attributable to interest income, debt investments, net (as a percent) 1.70% 2.20% 1.70% 2.00%    
Number of operating segments | segment     1      
Number of reportable segments | segment     1      
Revolving Credit Facility | Line of Credit            
Schedule of Investments [Line Items]            
Commitment fee (as a percentage)     3.40%      
Investment Owned, At Fair Value | Investment Type Concentration Risk            
Schedule of Investments [Line Items]            
Concentration risk (as a percent)     100.00%   100.00%  
Investment Owned, At Fair Value | Investment Type Concentration Risk | Non-accrual Status            
Schedule of Investments [Line Items]            
Concentration risk (as a percent)     1.20%   0.90%  
Investment Owned, At Cost | Investment Type Concentration Risk            
Schedule of Investments [Line Items]            
Concentration risk (as a percent)     100.00%   100.00%  
Investment Owned, At Cost | Investment Type Concentration Risk | Non-accrual Status            
Schedule of Investments [Line Items]            
Concentration risk (as a percent)     3.60%   3.50%  
LMM portfolio investments            
Schedule of Investments [Line Items]            
Consultation period subsequent to initial investment (in months)     12 months      
Investment company, number of portfolio companies with annual third-party appraisal was obtained, reviewed and certified | company 18 16       70
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 (as a percent) 27.00% 24.00%       92.00%
Private Loan portfolio investments            
Schedule of Investments [Line Items]            
Consultation period subsequent to initial investment (in months)     12 months      
Investment company, number of portfolio companies with annual third-party appraisal was obtained, reviewed and certified | company 14 17       63
Percentage of portfolio with annual third-party appraisal was obtained, reviewed and certified (as a percent)           97.00%
Private Loan portfolio investments | Investment Owned, At Fair Value | Investment Type Concentration Risk            
Schedule of Investments [Line Items]            
Concentration risk (as a percent) 26.00% 24.00%       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) 95.00%   95.00%   97.00% 95.00%
Middle Market portfolio investments | Investment Owned, At Fair Value | Investment Type Concentration Risk            
Schedule of Investments [Line Items]            
Concentration risk (as a percent)     1.70%   3.10%  
Middle Market portfolio investments | Investment Owned, At Cost | Investment Type Concentration Risk            
Schedule of Investments [Line Items]            
Concentration risk (as a percent)     2.80%   4.60%  
Other Portfolio investments | Investment Owned, At Fair Value | Investment Type Concentration Risk            
Schedule of Investments [Line Items]            
Concentration risk (as a percent)     2.40%   2.50%  
Other Portfolio investments | Investment Owned, At Cost | Investment Type Concentration Risk            
Schedule of Investments [Line Items]            
Concentration risk (as a percent)     3.00%   2.90%