Quarterly report pursuant to Section 13 or 15(d)

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

v3.22.2.2
FAIR VALUE HIERARCHY FOR INVESTMENTS—PORTFOLIO COMPOSITION - Narrative (Details)
$ in Thousands
 3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2022
USD ($)
investment
company
Sep. 30, 2021
USD ($)
Sep. 30, 2022
USD ($)
investment
company
Sep. 30, 2021
USD ($)
Dec. 31, 2021
USD ($)
company
investment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Expenses allocated $ 3,334 $ 2,728 $ 9,613 $ 7,680  
Annualized total return on investments 0.105 0.180 0.096 0.166  
Achieved total return on investments         0.166
Cost $ 3,689,627 $ 3,689,627 [1],[2],[3] $ 3,689,627 $ 3,689,627 [1],[2],[3] $ 3,259,246 [1],[4],[5]
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 $ 3,300 $ 2,700 $ 9,600 $ 7,700  
Short-term portfolio investments          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Number of investments | investment 1   1   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 75   75   73
Fair value $ 1,910,900   $ 1,910,900   $ 1,716,400
Cost 1,593,700   $ 1,593,700   $ 1,455,700
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     80.00% 70.00%  
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     73.00%   70.90%
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 87   87   75
Fair value $ 1,476,900   $ 1,476,900   $ 1,141,800
Cost 1,523,800   $ 1,523,800   $ 1,157,500
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     50.00% 57.00%  
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     97.10%   95.70%
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 33   33   36
Fair value $ 354,300   $ 354,300   $ 395,200
Cost 419,400   $ 419,400   $ 440,900
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     94.40%   93.30%
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 | company 14   14   13
Fair value $ 117,000   $ 117,000   $ 166,100
Cost 121,300   $ 121,300   $ 173,700
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     2.90%   4.70%
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     3.30%   5.30%
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 investments          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Fair value 112,500   $ 112,500   $ 140,400
Cost $ 29,500   $ 29,500   $ 29,500
External Investment Manager 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     2.80%   3.90%
External Investment Manager 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     0.80%   0.90%
[1] All investments are Lower Middle Market portfolio investments, unless otherwise noted. See Note C—Fair Value Hierarchy for Investments—Portfolio Composition for a description of Lower Middle Market portfolio investments. All of the Company’s investments, unless otherwise noted, are encumbered either as security for the Company’s Credit Facility or in support of the SBA-guaranteed debentures issued by the Funds.
[2] All portfolio company headquarters are based in the United States, unless otherwise noted.
[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] All portfolio company headquarters are based in the United States, unless otherwise noted.
[5] Principal is net of repayments. Cost is net of repayments and accumulated unearned income.