Quarterly report pursuant to Section 13 or 15(d)

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

v3.23.2
FAIR VALUE HIERARCHY FOR INVESTMENTS—PORTFOLIO COMPOSITION - Narrative (Details)
$ in Thousands
 3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2023
USD ($)
company
entity
Jun. 30, 2022
USD ($)
Jun. 30, 2023
USD ($)
company
entity
Jun. 30, 2022
USD ($)
Dec. 31, 2022
USD ($)
entity
company
investment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Expenses allocated $ 5,688 $ 3,462 $ 10,686 $ 6,279  
Annualized total return on investments 0.167 0.065 0.151 0.092  
Achieved total return on investments         0.111
Fair value $ 4,210,543 $ 4,210,543 [1] $ 4,210,543 $ 4,210,543 [1] $ 4,102,177 [2]
Cost 3,742,689 3,742,689 [3] $ 3,742,689 3,742,689 [3] $ 3,773,752 [4]
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     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     100.00%   100.00%
Affiliated Entity | External Investment Manager          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Expenses allocated $ 5,700 $ 3,500 $ 10,700 $ 6,300  
Short-term portfolio investments          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Number of investments | investment         1
Short-term portfolio investments | Maximum | Debt          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Investment term     1 year    
LMM portfolio investments          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Number of portfolio companies | company 79   79   78
Fair value $ 2,170,200   $ 2,170,200   $ 2,060,500
Cost 1,720,900   $ 1,720,900   $ 1,719,900
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     52.00% 54.00%  
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, percentage     72.00%   73.70%
LMM portfolio investments | Minimum          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Annual revenues     $ 10,000    
Investments 5,000   $ 5,000    
LMM portfolio investments | Minimum | Debt          
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 $ 75,000   $ 75,000    
LMM portfolio investments | Maximum | Debt          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Investment term     7 years    
Private Loan portfolio investments          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Number of portfolio companies | company 88   88   85
Fair value $ 1,499,300   $ 1,499,300   $ 1,471,500
Cost 1,519,900   $ 1,519,900   $ 1,500,300
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, percentage     49.00% 44.00%  
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, percentage     96.10%   97.10%
Private Loan portfolio investments | Minimum          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Investments 10,000   $ 10,000    
Private Loan portfolio investments | Minimum | Debt          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Investment term     3 years    
Private Loan portfolio investments | Maximum          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Investments $ 75,000   $ 75,000    
Private Loan portfolio investments | Maximum | Debt          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Investment term     7 years    
Middle Market portfolio investments          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Number of portfolio companies | company 28   28   31
Fair value $ 295,900   $ 295,900   $ 329,100
Cost 352,900   $ 352,900   $ 401,700
Middle Market 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, percentage     92.90%   93.80%
Middle Market portfolio investments | Minimum          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Annual revenues     $ 150,000    
Investments 3,000   $ 3,000    
Middle Market portfolio investments | Minimum | Debt          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Investment term     3 years    
Middle Market portfolio investments | Maximum          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Annual revenues     $ 1,500,000    
Investments $ 25,000   $ 25,000    
Middle Market portfolio investments | Maximum | Debt          
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 companies | entity 15   15   14
Fair value $ 111,200   $ 111,200   $ 116,300
Cost 119,400   $ 119,400   $ 120,400
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     2.60%   2.80%
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     3.20%   3.20%
Other Portfolio investments | Minimum | Debt          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Investment term     5 years    
Other Portfolio investments | Maximum | Debt          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Investment term     10 years    
External Investment Manager          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Fair value 134,000   $ 134,000   $ 122,900
Cost $ 29,500   $ 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, percentage     3.20%   3.00%
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, percentage     0.80%   0.80%
[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.