Quarterly report pursuant to Section 13 or 15(d)

FAIR VALUE HIERARCHY FOR INVESTMENTS???PORTFOLIO COMPOSITION - Changes in Fair Value of Level??3 Portfolio Investments (Details)

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FAIR VALUE HIERARCHY FOR INVESTMENTS—PORTFOLIO COMPOSITION - Changes in Fair Value of Level 3 Portfolio Investments (Details) - USD ($)
$ in Thousands
 9 Months Ended
Sep. 30, 2022
Sep. 30, 2021
Investments    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance $ 3,559,837 $ 2,684,866
Transfers Into Level 3 Hierarchy 0 0
Redemptions/ Repayments (486,293) (592,493)
New Investments 916,689 863,044
Other 0 0
Ending balance 3,971,635 3,082,763
Investments | Net Changes from Unrealized to Realized    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings (2,784) 8,513
Investments | Net Unrealized Appreciation (Depreciation)    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings (15,815) 118,833
Debt    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance 2,509,568 1,807,134
Transfers Into Level 3 Hierarchy 0 0
Redemptions/ Repayments (436,372) (528,158)
New Investments 869,214 814,863
Other (6,933) (3,485)
Ending balance 2,866,399 2,105,748
Debt | Net Changes from Unrealized to Realized    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings 9,632 13,279
Debt | Net Unrealized Appreciation (Depreciation)    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings (78,710) 2,115
Equity    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance 1,043,709 866,734
Transfers Into Level 3 Hierarchy 0 0
Redemptions/ Repayments (49,447) (64,335)
New Investments 47,475 48,181
Other 6,933 5,767
Ending balance 1,100,460 969,295
Equity | Net Changes from Unrealized to Realized    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings (11,801) (2,826)
Equity | Net Unrealized Appreciation (Depreciation)    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings 63,591 115,774
Equity Warrant    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance 6,560 10,998
Transfers Into Level 3 Hierarchy 0 0
Redemptions/ Repayments (474) 0
New Investments 0 0
Other 0 (2,282)
Ending balance 4,775 7,720
Equity Warrant | Net Changes from Unrealized to Realized    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings (615) (1,940)
Equity Warrant | Net Unrealized Appreciation (Depreciation)    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings $ (696) $ 944