Quarterly report pursuant to Section 13 or 15(d)

FAIR VALUE HIERARCHY FOR INVESTMENTS???PORTFOLIO COMPOSITION - Summary of Investments (Details)

v3.23.1
FAIR VALUE HIERARCHY FOR INVESTMENTS—PORTFOLIO COMPOSITION - Summary of Investments (Details)
$ in Thousands
 3 Months Ended 12 Months Ended
Mar. 31, 2023
USD ($)
company
Dec. 31, 2022
USD ($)
company
Mar. 31, 2022
USD ($)
Summary of Investment Holdings [Line Items]      
Fair value $ 4,160,917 $ 4,102,177 [1] $ 4,160,917 [2]
Cost $ 3,797,714 $ 3,773,752 [3] $ 3,797,714 [4]
Investment Owned, At Cost | Investment Type Concentration Risk      
Summary of Investment Holdings [Line Items]      
Concentration risk, percentage 100.00% 100.00%  
Non-accrual Status | Investment Owned, At Cost | Investment Type Concentration Risk      
Summary of Investment Holdings [Line Items]      
Concentration risk, percentage 3.20% 3.70%  
Equity | Investment Owned, At Cost | Investment Type Concentration Risk      
Summary of Investment Holdings [Line Items]      
Concentration risk, percentage 14.60% 14.20%  
First lien debt | Investment Owned, At Cost | Investment Type Concentration Risk      
Summary of Investment Holdings [Line Items]      
Concentration risk, percentage 84.70% 85.00%  
LMM portfolio investments      
Summary of Investment Holdings [Line Items]      
Number of portfolio companies | company 79 78  
Fair value $ 2,112,600 $ 2,060,500  
Cost $ 1,727,900 $ 1,719,900  
Weighted-average annual effective yield 12.60% 12.30%  
Average EBITDA $ 8,300 $ 8,000  
Diluted equity ownership percentage 41.00% 41.00%  
Investment company, number of companies within portfolio excluded from EBITDA calculation | company 4 3  
LMM portfolio investments | Non-accrual Status      
Summary of Investment Holdings [Line Items]      
Weighted-average annual effective yield 12.20% 11.60%  
LMM portfolio investments | Debt | Investment Owned, At Cost | Investment Type Concentration Risk      
Summary of Investment Holdings [Line Items]      
Concentration risk, percentage 72.90% 73.70%  
LMM portfolio investments | Equity | Investment Owned, At Cost | Investment Type Concentration Risk      
Summary of Investment Holdings [Line Items]      
Concentration risk, percentage 27.10% 26.30%  
LMM portfolio investments | First lien debt | Investment Owned, At Cost | Investment Type Concentration Risk      
Summary of Investment Holdings [Line Items]      
Concentration risk, percentage 99.20% 99.10%  
Private Loan portfolio investments      
Summary of Investment Holdings [Line Items]      
Number of portfolio companies | company 86 85  
Fair value $ 1,491,400 $ 1,471,500  
Cost $ 1,527,600 $ 1,500,300  
Weighted-average annual effective yield 12.40% 11.60%  
Average EBITDA $ 38,100 $ 38,100  
Investment company, number of companies within portfolio excluded from EBITDA calculation | company 2 2  
Private Loan portfolio investments | Non-accrual Status      
Summary of Investment Holdings [Line Items]      
Weighted-average annual effective yield 12.00% 11.20%  
Private Loan portfolio investments | Debt | Investment Owned, At Cost | Investment Type Concentration Risk      
Summary of Investment Holdings [Line Items]      
Concentration risk, percentage 97.10% 97.10%  
Private Loan portfolio investments | Equity | Investment Owned, At Cost | Investment Type Concentration Risk      
Summary of Investment Holdings [Line Items]      
Concentration risk, percentage 2.90% 2.90%  
Private Loan portfolio investments | First lien debt | Investment Owned, At Cost | Investment Type Concentration Risk      
Summary of Investment Holdings [Line Items]      
Concentration risk, percentage 99.50% 99.60%  
Middle Market portfolio investments      
Summary of Investment Holdings [Line Items]      
Number of portfolio companies | company 30 31  
Fair value $ 306,200 $ 329,100  
Cost $ 391,000 $ 401,700  
Weighted-average annual effective yield 11.80% 11.00%  
Average EBITDA $ 65,400 $ 68,700  
Middle Market portfolio investments | Non-accrual Status      
Summary of Investment Holdings [Line Items]      
Weighted-average annual effective yield 10.40% 10.30%  
Middle Market portfolio investments | Debt | Investment Owned, At Cost | Investment Type Concentration Risk      
Summary of Investment Holdings [Line Items]      
Concentration risk, percentage 93.60% 93.80%  
Middle Market portfolio investments | Equity | Investment Owned, At Cost | Investment Type Concentration Risk      
Summary of Investment Holdings [Line Items]      
Concentration risk, percentage 6.40% 6.20%  
Middle Market portfolio investments | First lien debt | Investment Owned, At Cost | Investment Type Concentration Risk      
Summary of Investment Holdings [Line Items]      
Concentration risk, percentage 99.30% 98.80%  
[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.