Quarterly report pursuant to Section 13 or 15(d)

Fair Value of Financial Instruments - Summary of Reconciliation of Changes for All Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Details)

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Fair Value of Financial Instruments - Summary of Reconciliation of Changes for All Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - Recurring - Significant Unobservable Inputs (Level 3) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 31, 2024
Mar. 31, 2023
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance $ 3,185,103 $ 2,882,285
Net realized gains (losses) 917 (832)
Net change in unrealized appreciation (depreciation) 1,539 25,766
Purchases 502,158 364,052
Sales (16,063) (312)
Repayments (174,035) (209,666)
Gross Transfers into Level 3 0 0
Gross Transfers out of Level 3 0 0
Ending balance 3,499,619 3,061,293
Preferred Stock    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance 53,038 41,488
Net realized gains (losses) 0  
Net change in unrealized appreciation (depreciation) (2,326) (1,143)
Purchases 1,597  
Ending balance 52,309 40,345
Common Stock    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance 41,790 25,059
Net change in unrealized appreciation (depreciation) (1,752) 5,632
Purchases 0  
Sales 0 (207)
Ending balance 40,038 30,484
Warrants    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance 22,088 19,419
Net realized gains (losses) 904 (858)
Net change in unrealized appreciation (depreciation) (2,113) 1,508
Purchases 1,232 948
Sales (2,829) (7)
Ending balance 19,282 21,010
Escrow and Other Investment Receivables    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance 10,888  
Net realized gains (losses) 13  
Net change in unrealized appreciation (depreciation) 7,353  
Purchases 0  
Sales (13,234)  
Ending balance 5,020  
Senior Secured Debt    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance 2,987,577 2,741,388
Net realized gains (losses) 0  
Net change in unrealized appreciation (depreciation) (104) 16,023
Purchases 498,787 362,781
Repayments (174,035) (209,666)
Ending balance 3,312,225 2,910,526
Unsecured Debt    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance 69,722 54,056
Net change in unrealized appreciation (depreciation) 481 3,746
Purchases 542 323
Ending balance $ 70,745 58,125
Escrow Receivable    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance   875
Net realized gains (losses)   26
Sales   (98)
Ending balance   $ 803