v3.26.3
FAIR VALUE HIERARCHY FOR INVESTMENTS—PORTFOLIO COMPOSITION - Schedule of Changes in Fair Value of Level 3 Portfolio Investments (Details) - USD ($)
$ in Thousands
 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Investments    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance $ 5,496,705 $ 4,932,669
Transfers Into (Out of) Level 3 Hierarchy 0 (16,810)
Redemptions/ Repayments (761,906) (788,769)
New Investments 990,701 892,115
Other 0 0
Ending balance 5,775,899 5,129,440
Net change in unrealized appreciation (depreciation) on assets still held 75,482 82,028
Investments | Income Statement Location [Axis]: us-gaap:DebtAndEquitySecuritiesRealizedGainLoss    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings (28,227) (10,479)
Investments | Income Statement Location [Axis]: us-gaap:DebtAndEquitySecuritiesUnrealizedGainLoss    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings 78,626 120,714
Debt    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance 3,607,331 3,278,365
Transfers Into (Out of) Level 3 Hierarchy 0 0
Redemptions/ Repayments (695,682) (740,766)
New Investments 903,391 785,187
Other (20,551) (37,295)
Ending balance 3,768,829 3,312,777
Net change in unrealized appreciation (depreciation) on assets still held (39,375) (16,369)
Debt | Income Statement Location [Axis]: us-gaap:DebtAndEquitySecuritiesRealizedGainLoss    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings 28,469 51,588
Debt | Income Statement Location [Axis]: us-gaap:DebtAndEquitySecuritiesUnrealizedGainLoss    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings (54,129) (24,302)
Equity    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance 1,858,205 1,637,181
Transfers Into (Out of) Level 3 Hierarchy 0 (16,810)
Redemptions/ Repayments (66,224) (48,003)
New Investments 87,310 106,928
Other 20,551 37,295
Ending balance 1,980,731 1,787,450
Net change in unrealized appreciation (depreciation) on assets still held 119,687 86,307
Equity | Income Statement Location [Axis]: us-gaap:DebtAndEquitySecuritiesRealizedGainLoss    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings (56,696) (62,067)
Equity | Income Statement Location [Axis]: us-gaap:DebtAndEquitySecuritiesUnrealizedGainLoss    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings 137,585 132,926
Equity warrants    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance 31,169 17,123
Transfers Into (Out of) Level 3 Hierarchy 0 0
Redemptions/ Repayments 0 0
New Investments 0 0
Other 0 0
Ending balance 26,339 29,213
Net change in unrealized appreciation (depreciation) on assets still held (4,830) 12,090
Equity warrants | Income Statement Location [Axis]: us-gaap:DebtAndEquitySecuritiesRealizedGainLoss    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings 0 0
Equity warrants | Income Statement Location [Axis]: us-gaap:DebtAndEquitySecuritiesUnrealizedGainLoss    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings $ (4,830) $ 12,090