Annual report pursuant to Section 13 and 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) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2022
Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Unrealized Gain (Loss) on Investments Unrealized Gain (Loss) on Investments
HTGC Debt And Equity Securities Realized Gain Loss    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Realized Investment Gains Losses Realized Investment Gains Losses
Recurring | Level 3 significant unobservable inputs    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Beginning Balance $ 2,329,044 $ 2,202,362
Net Realized Gains (Losses) [1] 5,785 (56,814)
Purchases [2] 1,162,985 1,366,339
Sales 98,584 13,379
Repayments [3] 461,193 1,208,548
Gross Transfers into Level 3 207 [4] 0 [5]
Gross Transfers out of Level 3 13,868 [4] 30,795 [5]
Ending Balance 2,882,285 2,329,044
Recurring | Level 3 significant unobservable inputs | Escrow Receivables    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Beginning Balance 561 65
Net Realized Gains (Losses) [1] 401 585
Purchases [2] 1,148 2,494
Sales 948 1,043
Repayments [3] 0 0
Gross Transfers into Level 3 0 [4] 0 [5]
Gross Transfers out of Level 3 0 [4] 0 [5]
Ending Balance 875 561
Recurring | Level 3 significant unobservable inputs | Unsecured Debt [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Beginning Balance 52,890 14,970
Purchases [2] 4,006 39,575
Sales 0 0
Repayments [3] 0 0
Gross Transfers into Level 3 0 [4] 0 [5]
Gross Transfers out of Level 3 0 [4] 0 [5]
Ending Balance 54,056 52,890
Recurring | Level 3 significant unobservable inputs | Senior Secured Debt    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Beginning Balance 2,156,709 2,079,465
Net Realized Gains (Losses) [1] (1,884) (3,744)
Purchases [2] 1,145,048 1,294,669
Sales 84,000 0
Repayments [3] 461,193 1,208,548
Gross Transfers into Level 3 [4] 0  
Gross Transfers out of Level 3 3,504 [4] 2,299 [5]
Ending Balance 2,741,388 2,156,709
Recurring | Level 3 significant unobservable inputs | Preferred Stock    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Beginning Balance 69,439 58,981
Net Realized Gains (Losses) [1] 7,966 158
Purchases [2] 5,264 21,180
Sales 11,101 62,897
Repayments [3] 0 0
Gross Transfers into Level 3 0 [4] 0 [5]
Gross Transfers out of Level 3 6,422 [4] 1,267 [5]
Ending Balance 41,488 69,439
Recurring | Level 3 significant unobservable inputs | Common Stock    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Beginning Balance 21,968 27,398
Net Realized Gains (Losses) [1] (74) (60,904)
Purchases [2] 25 4,371
Sales 19 (60,900)
Repayments [3] 0 0
Gross Transfers into Level 3 207 [4] 0 [5]
Gross Transfers out of Level 3 3,942 [4] 25,460 [5]
Ending Balance 25,059 21,968
Recurring | Level 3 significant unobservable inputs | Warrant [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Beginning Balance 27,477 21,483
Net Realized Gains (Losses) [1] (624) 7,091
Purchases [2] 7,494 4,050
Sales 2,516 10,339
Repayments [3] 0 0
Gross Transfers into Level 3 0 [4] 0 [5]
Gross Transfers out of Level 3 (0) [4] 1,769 [5]
Ending Balance 19,419 27,477
Recurring | Debt And Equity Securities Unrealized Gain Loss | Level 3 significant unobservable inputs    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Net Change in Unrealized Appreciation (Depreciation) [6] (42,091) 69,879
Recurring | Debt And Equity Securities Unrealized Gain Loss | Level 3 significant unobservable inputs | Escrow Receivables    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Net Change in Unrealized Appreciation (Depreciation) [6] (287) (1,540)
Recurring | Debt And Equity Securities Unrealized Gain Loss | Level 3 significant unobservable inputs | Unsecured Debt [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Net Change in Unrealized Appreciation (Depreciation) [6] (2,840) (1,655)
Recurring | Debt And Equity Securities Unrealized Gain Loss | Level 3 significant unobservable inputs | Senior Secured Debt    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Net Change in Unrealized Appreciation (Depreciation) [6] (9,788) (2,834)
Recurring | Debt And Equity Securities Unrealized Gain Loss | Level 3 significant unobservable inputs | Preferred Stock    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Net Change in Unrealized Appreciation (Depreciation) [6] (23,658) 53,284
Recurring | Debt And Equity Securities Unrealized Gain Loss | Level 3 significant unobservable inputs | Common Stock    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Net Change in Unrealized Appreciation (Depreciation) [6] 6,894 15,663
Recurring | Debt And Equity Securities Unrealized Gain Loss | Level 3 significant unobservable inputs | Warrant [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Net Change in Unrealized Appreciation (Depreciation) [6] $ (12,412) $ 6,961
[1] Included in net realized gains (losses) in the accompanying Consolidated Statements of Operations.
[2] Amounts listed above are inclusive of loan origination fees received at the inception of the loan which are deferred and amortized into fee income as well as the accretion of existing loan discounts and fees during the period. Escrow receivable purchases may include additions due to proceeds held in escrow from the liquidation of level 3 investments. Amounts are net of purchases assigned to the Adviser Funds.
[3] Amounts listed above include the acceleration and payment of loan discounts and loan fees due to early payoffs or restructures along with regularly scheduled amortization.
[4] Transfers out of Level 3 during the year ended December 31, 2022 related to the initial public offerings of Gelesis, Inc., Pineapple Energy, LLC, and the
conversion of Level 3 debt investments into common stock investments. Transfers into Level 3 during the year ended December 31, 2022 related to the
decline of liquidity of Kaleido Biosciences, Inc. shares.
[5] Transfers out of Level 3 during the year ended December 31, 2021 relate to the initial public offerings of Proterra, Inc., 23andMe, Inc., Sprinklr, Inc., Century Therapeutics, Couchbase, Inc., Xometry, Inc., and Nextdoor.com, Inc. and the conversion of Level 3 debt investments into common stock investments. There were no transfers into Level 3 during the year ended December 31, 2021 related to the conversion of Level 3 debt investments into equity investments and other assets.
[6] Included in net change in unrealized appreciation (depreciation) in the accompanying Consolidated Statements of Operations.