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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
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Dec. 31, 2024 | Dec. 31, 2023
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] | Net realized gain (loss) | Net realized gain (loss)
Significant Unobservable Inputs (Level 3) | Recurring |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Roll Forward] |  |
Beginning Balance | $ 3,185,103 | $ 2,882,285
Net Realized Gains (Losses) | (65,781) | (13,021)
Net Change in Unrealized Appreciation (Depreciation) | (10,738) | 19,550
Purchases | 1,494,274 | 1,289,369
Sales | (22,693) | (2,632)
Repayments | (965,924) | (990,448)
Gross Transfers into Level 3 | (2,323) | (39,979)
Gross Transfers out of Level 3 | (2,605) | (39,979)
Ending Balance | 3,613,959 | 3,185,103
Significant Unobservable Inputs (Level 3) | Recurring | Accounts Payable and Accrued Liabilities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Roll Forward] |  |
Beginning Balance | 0 |
Net Realized Gains (Losses) | (10,938) |
Net Change in Unrealized Appreciation (Depreciation) | 11,179 |
Purchase | 1,870 |
Sales | 1,353 |
Repayments | 0 |
Gross Transfers into Level 3 | 1,770 |
Gross Transfers out of Level 3 | 0 |
Ending Balance | 1,012 | 0
Significant Unobservable Inputs (Level 3) | Recurring | Preferred Stock |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Roll Forward] |  |
Beginning Balance | 53,038 | 41,488
Net Realized Gains (Losses) | (711) | (3,441)
Net Change in Unrealized Appreciation (Depreciation) | (5,709) | (1,123)
Purchases | 4,753 | 2,851
Sales | 0 | 0
Repayments | 0 | 0
Gross Transfers into Level 3 | (2,431) | (13,263)
Gross Transfers out of Level 3 | 0 | 0
Ending Balance | 53,802 | 53,038
Significant Unobservable Inputs (Level 3) | Recurring | Common Stock |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Roll Forward] |  |
Beginning Balance | 41,790 | 25,059
Net Realized Gains (Losses) | (1,453) | 0
Net Change in Unrealized Appreciation (Depreciation) | (1,506) | 11,325
Purchases | 4,100 | 6,000
Sales | 0 | (594)
Repayments | 0 | 0
Gross Transfers into Level 3 | (1,662) | 0
Gross Transfers out of Level 3 | 0 | 0
Ending Balance | 44,593 | 41,790
Significant Unobservable Inputs (Level 3) | Recurring | Warrants |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Roll Forward] |  |
Beginning Balance | 22,088 | 19,419
Net Realized Gains (Losses) | (648) | (4,295)
Net Change in Unrealized Appreciation (Depreciation) | (702) | 4,825
Purchases | 3,914 | 3,894
Sales | (2,829) | (1,755)
Repayments | 0 | 0
Gross Transfers into Level 3 | 0 | 0
Gross Transfers out of Level 3 | 0 | 0
Ending Balance | 21,823 | 22,088
Significant Unobservable Inputs (Level 3) | Recurring | Senior Secured Debt |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Roll Forward] |  |
Beginning Balance | 2,987,577 | 2,741,388
Net Realized Gains (Losses) | (52,120) | (5,350)
Net Change in Unrealized Appreciation (Depreciation) | (21,146) | 17,277
Purchases | 1,475,032 | 1,264,689
Sales | 0 | 0
Repayments | (965,924) | (990,448)
Gross Transfers into Level 3 | 0 | 0
Gross Transfers out of Level 3 | (4,375) | (39,979)
Ending Balance | 3,419,044 | 2,987,577
Significant Unobservable Inputs (Level 3) | Recurring | Unsecured Debt |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Roll Forward] |  |
Beginning Balance | 69,722 | 54,056
Net Realized Gains (Losses) | 0 | 0
Net Change in Unrealized Appreciation (Depreciation) | 1,277 | 4,268
Purchases | 4,558 | 11,398
Sales | 0 | 0
Repayments | 0 | 0
Gross Transfers into Level 3 | 0 | 0
Gross Transfers out of Level 3 | 0 | 0
Ending Balance | 75,557 | 69,722
Significant Unobservable Inputs (Level 3) | Recurring | Escrow and Other Investment Receivables |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Roll Forward] |  |
Beginning Balance | 10,888 | 875
Net Realized Gains (Losses) | 89 | 65
Net Change in Unrealized Appreciation (Depreciation) | 5,869 | (17,022)
Purchases | 47 | 537
Sales | (18,511) | (283)
Repayments | 0 | 0
Gross Transfers into Level 3 | 0 | (26,716)
Gross Transfers out of Level 3 | 1,770 | 0
Ending Balance | $ 152 | $ 10,888
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)

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