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

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

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FAIR VALUE HIERARCHY FOR INVESTMENTS—PORTFOLIO COMPOSITION - Narrative (Details)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
USD ($)
investmentManager
entity
Dec. 31, 2023
USD ($)
investmentManager
entity
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Achieved total return on investments 0.124 0.136
Fair value $ 1,177,507 [1] $ 1,092,895 [2]
Cost $ 1,138,745 [3] $ 1,038,318 [4]
Concentration risk, percentage (as a percent) 100.00% 100.00%
Investment Owned, At Fair Value | Investment Type Concentration Risk    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Concentration risk, percentage (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, percentage (as a percent) 100.00% 100.00%
Private Loan    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value $ 677,900 $ 595,300
Cost $ 697,500 $ 586,400
Private Loan | Investment Owned, At Fair Value | Investment Type Concentration Risk    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Concentration risk, percentage (as a percent) 85.00% 79.00%
Private Loan | Debt investments | Investment Owned, At Cost | Investment Type Concentration Risk    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Concentration risk, percentage (as a percent) 93.90% 94.10%
Private Loan | Minimum    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Annual revenues $ 25,000  
Investments $ 1,000  
Private Loan | Minimum | Debt investments    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investment, term 3 years  
Private Loan | Maximum    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Annual revenues $ 500,000  
Investments $ 30,000  
Private Loan | Maximum | Debt investments    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investment, term 7 years  
LMM portfolio investments    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value $ 436,100 $ 387,000
Cost $ 357,100 $ 315,700
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, percentage (as a percent) 92.00% 95.00%
LMM portfolio investments | Debt investments | Investment Owned, At Cost | Investment Type Concentration Risk    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Concentration risk, percentage (as a percent) 67.80% 70.20%
LMM portfolio investments | Minimum    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Annual revenues $ 10,000  
Investments $ 1,000  
LMM portfolio investments | Minimum | Debt investments    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investment, term 5 years  
LMM portfolio investments | Maximum    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Annual revenues $ 150,000  
Investments $ 30,000  
LMM portfolio investments | Maximum | Debt investments    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investment, term 7 years  
Middle Market    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value $ 39,400 $ 86,000
Cost $ 66,300 $ 114,700
Middle Market | Debt investments | Investment Owned, At Cost | Investment Type Concentration Risk    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Concentration risk, percentage (as a percent) 87.80% 93.10%
Middle Market | Minimum    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments $ 1,000  
Middle Market | Minimum | Debt investments    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investment, term 3 years  
Middle Market | Maximum    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments $ 20,000  
Middle Market | Maximum | Debt investments    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investment, term 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 6 6
Number of portfolio investments with investments managers | investmentManager 4 4
Fair value $ 24,100 $ 24,600
Cost $ 17,900 $ 21,500
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, percentage (as a percent) 2.00% 2.30%
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, percentage (as a percent) 1.60% 2.10%
Other Portfolio investments | Minimum | Debt investments    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investment, term 5 years  
Other Portfolio investments | Maximum | Debt investments    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investment, term 10 years  
[1] 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.
[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] 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.
[4] 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.