Annual report [Section 13 and 15(d), not S-K Item 405]

FAIR VALUE HIERARCHY FOR INVESTMENTS???PORTFOLIO COMPOSITION - Narrative (Details)

v3.25.4
FAIR VALUE HIERARCHY FOR INVESTMENTS—PORTFOLIO COMPOSITION - Narrative (Details)
$ in Thousands
 12 Months Ended
Dec. 31, 2025
USD ($)
company
investmentManager
investment
entity
Dec. 31, 2024
USD ($)
entity
company
investmentManager
investment
Dec. 31, 2023
USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Expenses allocated $ 23,533 $ 23,088 $ 22,050
Achieved total return on investments (as a percent) 0.164 0.179  
Fair value $ 5,518,117 [1],[2],[3] $ 4,932,669 [4],[5],[6]  
Cost $ 4,724,528 [1],[3],[7] $ 4,237,312 [4],[6],[8]  
Investment Owned, At Fair Value | Investment Type Concentration Risk      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Concentration risk (as a percent) 100.00% 100.00%  
Investment Owned, At Cost | Investment Type Concentration Risk      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Concentration risk (as a percent) 100.00% 100.00%  
Affiliated Entity | External Investment Manager      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Expenses allocated $ 23,500 $ 23,100 $ 22,100
Short-term portfolio investments      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Number of portfolio investments | investment 0 0  
Short-term portfolio investments | Maximum | Debt      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Investment term (in years) 1 year    
LMM portfolio investments      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Fair value $ 3,057,000 $ 2,502,900  
Cost $ 2,419,300 $ 1,937,800  
Number of portfolio companies | company 92 84  
LMM portfolio investments | Investment Owned, At Fair Value | Investment Type Concentration Risk      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Concentration risk (as a percent) 88.00% 93.00%  
LMM portfolio investments | Debt | Investment Owned, At Cost | Investment Type Concentration Risk      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Concentration risk (as a percent) 71.20% 70.80%  
LMM portfolio investments | Minimum      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Annual revenues $ 10,000    
Investments $ 5,000    
LMM portfolio investments | Minimum | Debt      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Investment term (in years) 5 years    
LMM portfolio investments | Maximum      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Annual revenues $ 150,000    
Investments $ 125,000    
LMM portfolio investments | Maximum | Debt      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Investment term (in years) 7 years    
Private Loan portfolio investments      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Fair value $ 1,988,400 $ 1,904,300  
Cost $ 2,014,100 $ 1,952,500  
Number of portfolio companies | company 86 91  
Private Loan portfolio investments | Investment Owned, At Fair Value | Investment Type Concentration Risk      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Concentration risk (as a percent) 87.00% 85.00%  
Private Loan portfolio investments | Debt | Investment Owned, At Cost | Investment Type Concentration Risk      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Concentration risk (as a percent) 93.50% 95.40%  
Private Loan portfolio investments | Minimum      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Annual revenues $ 25,000    
Investments $ 10,000    
Private Loan portfolio investments | Minimum | Debt      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Investment term (in years) 3 years    
Private Loan portfolio investments | Maximum      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Annual revenues $ 500,000    
Investments $ 100,000    
Private Loan portfolio investments | Maximum | Debt      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Investment term (in years) 7 years    
Middle Market portfolio investments      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Fair value $ 83,500 $ 155,300  
Cost $ 120,100 $ 195,000  
Number of portfolio companies | company 11 15  
Middle Market portfolio investments | Investment Owned, At Fair Value | Investment Type Concentration Risk      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Concentration risk (as a percent) 1.50% 3.10%  
Middle Market portfolio investments | Investment Owned, At Cost | Investment Type Concentration Risk      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Concentration risk (as a percent) 2.50% 4.60%  
Middle Market portfolio investments | Minimum      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Investments $ 3,000    
Middle Market portfolio investments | Minimum | Debt      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Investment term (in years) 3 years    
Middle Market portfolio investments | Maximum      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Investments $ 25,000    
Middle Market portfolio investments | Maximum | Debt      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Investment term (in years) 7 years    
Other Portfolio investments      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Number of portfolio investments in entities | entity 33 31  
Number of investment managers | investmentManager 13 12  
Fair value $ 134,100 $ 124,100  
Cost $ 141,600 $ 122,500  
Other Portfolio investments | Investment Owned, At Fair Value | Investment Type Concentration Risk      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Concentration risk (as a percent) 2.40% 2.50%  
Other Portfolio investments | Investment Owned, At Cost | Investment Type Concentration Risk      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Concentration risk (as a percent) 3.00% 2.90%  
Other Portfolio investments | Minimum | Debt      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Investment term (in years) 5 years    
Other Portfolio investments | Maximum | Debt      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Investment term (in years) 10 years    
External Investment Manager      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Fair value $ 255,000 $ 246,000  
Cost $ 29,500 $ 29,500  
External Investment Manager | Investment Owned, At Fair Value | Investment Type Concentration Risk      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Concentration risk (as a percent) 4.60% 5.00%  
External Investment Manager | Investment Owned, At Cost | Investment Type Concentration Risk      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Concentration risk (as a percent) 0.60% 0.70%  
[1] All portfolio company headquarters are based in the U.S., unless otherwise noted.
[2] Investment Fair Value was determined using significant unobservable inputs, unless otherwise noted. See Note C — Fair Value Hierarchy for Investments —Portfolio Composition for further discussion. Negative fair value is the result of the capitalized discount on the loan or the unfunded commitment being valued below par.
[3] All investments are LMM (as defined below) portfolio investments, unless otherwise noted. See Note C — Fair Value Hierarchy for Investments — Portfolio Composition for a description of LMM portfolio investments. All of the Company’s investments, unless otherwise noted, are encumbered either as security for the Corporate Facility or SPV Facility (each as defined below) or in support of the debentures guaranteed by the SBA (as defined below) and issued by the Funds (as defined below).
[4] All portfolio company headquarters are based in the U.S., unless otherwise noted.
[5] Investment Fair Value was determined using significant unobservable inputs, unless otherwise noted. See Note C — Fair Value Hierarchy for Investments — Portfolio Composition for further discussion. Negative fair value is the result of the capitalized discount on the loan or the unfunded commitment being valued below par.
[6] All investments are LMM portfolio investments, unless otherwise noted. See Note C — Fair Value Hierarchy for Investments — Portfolio Composition for a description of LMM portfolio investments. All of the Company’s investments, unless otherwise noted, are encumbered either as security for the Corporate Facility or SPV Facility or in support of the debentures guaranteed by the SBA and issued by the Funds.
[7] Principal is net of repayments. Cost is net of repayments and accumulated unearned income. Negative cost is the result of the capitalized discount being greater than the principal amount outstanding on the loan.
[8] Principal is net of repayments. Cost is net of repayments and accumulated unearned income. Negative cost is the result of the capitalized discount being greater than the principal amount outstanding on the loan.