Annual report pursuant to Section 13 and 15(d)

Fair Value of Financial Instruments - Schedule 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 - Schedule of Reconciliation of Changes for All Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Roll Forward]    
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Total net realized gain (loss) Total net realized gain (loss)
HTGC Debt And Equity Securities Realized Gain Loss    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Roll Forward]    
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Total net change in unrealized appreciation (depreciation) Total net change in unrealized appreciation (depreciation)
Recurring | Significant Unobservable Inputs (Level 3)    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Roll Forward]    
Beginning Balance $ 2,882,285 $ 2,329,044
Net Realized Gains (Losses) (13,021) 5,785
Net Change in Unrealized Appreciation (Depreciation) 19,550 (42,091)
Purchases 1,289,369 1,162,985
Sales (2,632) (98,584)
Repayments (990,448) (461,193)
Gross Transfers into Level 3 39,979 207
Gross Transfers out of Level 3 (39,979) (13,868)
Ending Balance 3,185,103 2,882,285
Recurring | Significant Unobservable Inputs (Level 3) | Preferred Stock    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Roll Forward]    
Beginning Balance 41,488 69,439
Net Realized Gains (Losses) (3,441) 7,966
Net Change in Unrealized Appreciation (Depreciation) (1,123) (23,658)
Purchases 2,851 5,264
Sales 0 (11,101)
Repayments 0 0
Gross Transfers into Level 3 13,263 0
Gross Transfers out of Level 3 0 (6,422)
Ending Balance 53,038 41,488
Recurring | Significant Unobservable Inputs (Level 3) | Common Stock    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Roll Forward]    
Beginning Balance 25,059 21,968
Net Realized Gains (Losses) 0 (74)
Net Change in Unrealized Appreciation (Depreciation) 11,325 6,894
Purchases 6,000 25
Sales (594) (19)
Repayments 0 0
Gross Transfers into Level 3 0 207
Gross Transfers out of Level 3 0 (3,942)
Ending Balance 41,790 25,059
Recurring | Significant Unobservable Inputs (Level 3) | Warrants    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Roll Forward]    
Beginning Balance 19,419 27,477
Net Realized Gains (Losses) (4,295) (624)
Net Change in Unrealized Appreciation (Depreciation) 4,825 (12,412)
Purchases 3,894 7,494
Sales (1,755) (2,516)
Repayments 0 0
Gross Transfers into Level 3 0 0
Gross Transfers out of Level 3 0 0
Ending Balance 22,088 19,419
Recurring | Significant Unobservable Inputs (Level 3) | Senior Secured Debt    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Roll Forward]    
Beginning Balance 2,741,388 2,156,709
Net Realized Gains (Losses) (5,350) (1,884)
Net Change in Unrealized Appreciation (Depreciation) 17,277 (9,788)
Purchases 1,264,689 1,145,048
Sales 0 (84,000)
Repayments (990,448) (461,193)
Gross Transfers into Level 3 0 0
Gross Transfers out of Level 3 (39,979) (3,504)
Ending Balance 2,987,577 2,741,388
Recurring | Significant Unobservable Inputs (Level 3) | Unsecured Debt    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Roll Forward]    
Beginning Balance 54,056 52,890
Net Realized Gains (Losses) 0 0
Net Change in Unrealized Appreciation (Depreciation) 4,268 (2,840)
Purchases 11,398 4,006
Sales 0 0
Repayments 0 0
Gross Transfers into Level 3 0 0
Gross Transfers out of Level 3 0 0
Ending Balance 69,722 54,056
Recurring | Significant Unobservable Inputs (Level 3) | Escrow and Other Investment Receivable    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Roll Forward]    
Beginning Balance 875  
Net Realized Gains (Losses) 65  
Net Change in Unrealized Appreciation (Depreciation) (17,022)  
Purchases 537  
Sales (283)  
Repayments 0  
Gross Transfers into Level 3 26,716  
Gross Transfers out of Level 3 0  
Ending Balance 10,888 875
Recurring | Significant Unobservable Inputs (Level 3) | Escrow Receivable    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Roll Forward]    
Beginning Balance $ 875 561
Net Realized Gains (Losses)   401
Net Change in Unrealized Appreciation (Depreciation)   (287)
Purchases   1,148
Sales   (948)
Repayments   0
Gross Transfers into Level 3   0
Gross Transfers out of Level 3   0
Ending Balance   $ 875