Document And Entity Information
Note To Financial Statement Details Textual
us-gaap_InvestmentCompanyIncentiveFeeWaived
Investment Company, Incentive Fee Waived
Significant Accounting Policies
Consolidated Schedule of Investments
Note 3 - Related Party Transactions
hrzn_IncreaseDecreaseInEndoftermPayments
Decrease (increase) in end-of-term payments
Amount of increase (decrease) in end-of-term payments.
Note 4 - Investments
hrzn_IncreaseDecreaseInUnearnedIncome
Decrease in unearned income
Amount of increase (decrease) in unearned income.
Note 5 - Transactions With Affiliated Companies
Warrant and equity investments received and recorded as unearned income
Amount of warrant investments received and recorded as unearned income.
Note 6 - Fair Value
End-of-term payments receivable
Amount of end-of-term payments receivable in noncash or part noncash transaction.
Note 7 - Borrowings
Note 8 - Federal Income Tax
Net investment income per common share - diluted (in dollars per share)
Note 9 - Financial Instruments With Off-balance-sheet Risk
Note 11 - Distributions
Note 12 - Earnings Per Share
Note 14 - Financial Highlights
Consolidated Schedule of Investments - Investments (Details)
Consolidated Schedule of Investments - Investments 2 (Details)
Consolidated Schedule of Investments - Investments (Details) (Parentheticals)
Note 3 - Related Party Transactions - Expiration Dates of Contingent Future Liability (Details)
Note 4 - Investments - Investments (Details)
March 31, 2027 Expiration [Member]
Represents information pertaining to the expiration of the total contingent future liability.
Note 5 - Transactions With Affiliated Companies - Investments in Controlled Affiliated Companies (Details)
Note 6 - Fair Value - Assets at Fair Value on a Recurring Basis (Details)
Note 6 - Fair Value - Significant Level 3 Fair Value Measurement Inputs (Details)
Note 6 - Fair Value - Reconciliation of Level 3 Assets Measured on a Recurring Basis (Details)
Note 7 - Borrowings - Borrowings (Details)
Note 7 - Borrowings - Senior Securities (Details)
Note 8 - Federal Income Tax - Reconciliation of Net Increase in Net Assets to Taxable Income (Details)
Avalo Therapeutics, Inc. [Member]
Represents Avalo Therapeutics, Inc.
Note 8 - Federal Income Tax - Tax Characters of Distributions Paid (Details)
Note 8 - Federal Income Tax - Undistributed Ordinary Income Earnings on a Tax Basis (Details)
Note 9 - Financial Instruments With Off-balance-sheet Risk - Unfunded Commitments (Details)
Note 11 - Distributions - Distribution Activity (Details)
Note 12 - Earnings Per Share - Schedule of Earnings Per share (Details)
Note 14 - Financial Highlights - Financial Highlights (Details)
hrzn_InvestmentsFairValueNonaccrualStatus
Investments, Fair Value, Nonaccrual Status
The fair value of investments on nonaccrual status.
Notes To Financial Statements
Notes To Financial Statements [Abstract]
Other Debt Obligations [Member]
Revolver Loan, Prime Index, Two [Member]
Represents information pertaining to the second revolver loans' prime index.
Two Investments [Member]
Related to two investments.
hrzn_InvestmentsCostNonaccrualStatus
Investments, Cost, Nonaccrual Status
The cost value of investments on nonaccrual status.
hrzn_InvestmentNonaccrualIncomeNotReceivedInCashPercent
Investment, Nonaccrual, Income Not Received in Cash, Percent
The percent of nonaccrual investment income not received in cash.
Other Investments, Prime Index, Two [Member]
Represents other investments with prime index.
Other Investments, Prime Index, One [Member]
Represents other investments with prime index.
One Investment [Member]
Related to one investment.
June 30, 2027 Expiration [Member]
Represents information pertaining to the expiration of the total contingent future liability.
Preferred Stock 2 [Member]
Preferred shares may provide a preferential dividend to the dividend on common stock and may take precedence over common stock in the event of a liquidation. Preferred shares typically represent an ownership interest in the company.
GT Medical Technologies, Inc. [Member]
Represents GT Medical Technologies, Inc.
Equity Securities [Member]
Other Investments, Prime Index, Four [Member]
Represents other investments with prime index.
Other Investments, Prime Index, Three [Member]
Represents other investments with prime index.
Other Investments, Prime Index, Six [Member]
Represents other investments with prime index.
Other Investments, Prime Index, Five [Member]
Represents other investments with prime index.
Fictiv, Inc. [Member]
Represents Fictiv, Inc.
Pivot Bio, Inc. [Member]
Represents Pivot Bio, Inc.
Monroe Capital Intermediate Holdings, LLC [Member]
Pertains to the related parties.
hrzn_OwnershipPercentageAcquired
Ownership Percentage
Pertains to the percentage of ownership acquired.
Equity Purchase Agreement [Member]
Pertains to the type of arrangement.
Castle Creek Biosciences, Inc [Member]
Represents Castle Creek Biosciences, Inc.
Financial Instruments [Domain]
Standvast Holdings, LLC [Member]
Related to Standvast Holdings, LLC.
Debt [Member]
Emalex Biosciences, Inc. [Member]
Represents Emalex Biosciences, Inc.
Multiple Probability Weighted Scenario Model [Member]
Related to Multiple Probability Weighted Scenario Model.
Financial Instrument [Axis]
Term Loan, Prime Index, One [Member]
Represents term loan with prime index.
Provivi, Inc. [Member]
Represents Provivi, Inc.
Greenlight Biosciences, Inc [Member]
Represents Greenlight Biosciences, Inc.
O 2024 M7 1 Dividends [Member]
Information regarding distributions.
O 2024 M7 3 Dividends [Member]
Information regarding distributions.
O 2024 M7 2 Dividends [Member]
Information regarding distributions.
Aerobiotix, LLC [Member]
Represents Aerobiotix, LLC.
us-gaap_PolicyTextBlockAbstract
Accounting Policies
Selected Interest Rates (Daily) [Member]
Represents the Selected Interest Rates (Daily).
InfoBionic, Inc [Member]
Represents InfoBionic, Inc.
hrzn_FederalExciseTaxPercent
Federal Excise Tax, Percent
The federal excise tax percent.
hrzn_DebtInstrumentBasisSpreadOnVariableRateTreasuryYieldMaturity
Debt Instrument, Basis Spread on Variable Rate, Treasury Yield Maturity (Year)
Period of maturity for treasury yield used to calculate basis spread on variable rate of debt instrument.
Magnolia Medical Technologies, Inc [Member]
Represents Magnolia Medical Technologies, Inc.
Conventus Orthopaedics, Inc [Member]
Represents Conventus Orthopaedics, Inc.
Nuveen Facility [Member]
Represents the Nuveen Facility.
CSA Medical, Inc [Member]
Represents CSA Medical, Inc.
The 2021 Equity Distribution Agreement [Member]
Related to the 2021 equity distribution agreement.
O 2024 M4 2 Dividends [Member]
Information regarding distributions.
hrzn_EquitySalesAgreementRemainingAmountAvailableForIssuance
Equity Sales Agreement, Remaining Amount Available for Issuance
The remaining amount available for issuance under equity sales agreement.
O 2024 M4 1 Dividends [Member]
Information regarding distributions.
hrzn_StockRepurchasedDuringPeriodPerShare
Stock Repurchased During Period, Per Share (in dollars per share)
Per share value of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.
O 2024 M2 1 Dividends [Member]
Information regarding distributions.
Distributions [Policy Text Block]
The disclosure for the accounting policy related to distributions.
O 2024 M4 3 Dividends [Member]
Information regarding distributions.
Spineology, Inc [Member]
Represents Spineology, Inc.
hrzn_EquitySalesAgreementMaximumValue
Equity Sales Agreement, Maximum Value
The maximum value issuable under equity sales agreement.
Stock Repurchase Program [Policy Text Block]
The accounting policy for stock repurchase program.
O 2024 M2 3 Dividends [Member]
Information regarding distributions.
Public Offering [Member]
Related to public offering.
O 2024 M2 2 Dividends [Member]
Information regarding dividends.
O 2024 M2 4 Dividends [Member]
Information regarding distributions.
Liabilities
Financial Instruments Disclosure [Text Block]
Consumer-related Technologies [Member]
Related to Consumer-related Technologies.
us-gaap_Assets
Total assets
Other Healthcare Sector [Member]
Related to other healthcare sector.
September 30, 2027 Expiration [Member]
Represents information pertaining to the expiration of the total contingent future liability.
Treasury Rate [Member]
Represents information pertaining to the treasury rate.
Other assets
Restricted investments in money market funds
Restricted Investments
Axiom Space, Inc [Member]
Represents Axiom Space, Inc.
Basis of Presentation and Significant Accounting Policies [Text Block]
Soli Organic, Inc [Member]
Represents Soli Organic, Inc.
Temperpack Technologies, Inc [Member]
Represents Temperpack Technologies, Inc.
O 2025 M2 2 Dividends [Member]
Information regarding distributions.
Alula Holdings, Inc [Member]
Represents Alula Holdings, Inc.
O 2025 M2 1 Dividends [Member]
Information regarding distributions.
March 31, 2028 Expiration [Member]
Represents information pertaining to the expiration of the total contingent future liability.
The 2031 Convertible Notes [Member]
Related to the Convertible Notes due 2031.
Term Loan, SOFR Index, One [Member]
Represents information pertaining to the first term loan with a SOFR index.
CAMP NYC, Inc [Member]
Represents CAMP NYC, Inc
Clara Foods Co [Member]
Represents Clara Foods Co.
O 2025 M2 3 Dividends [Member]
Information regarding distributions.
O 2025 M7 Dividends [Member]
Information regarding distributions.
Liqid, Inc [Member]
Represents Liqid, Inc.
Lyrical Foods, Inc [Member]
Represents Lyrical Foods, Inc.
Decisyon, Inc [Member]
Represents Decisyon, Inc.
MyForest Foods Co [Member]
Represents MyForest Foods Co.
NextCar Holding Company, Inc [Member]
Represents NextCar Holding Company, Inc.
Primary Kids, Inc [Member]
Represents Primary Kids, Inc.
Unagi, Inc [Member]
Represents Unagi, Inc.
Investments in and Advances to Affiliates, Schedule of Investments [Text Block]
hrzn_DebtInstrumentInterestRateIncreaseFromDefault
Debt Instrument, Interest Rate, Increase From Default
Pertains to the term of the agreement.
hrzn_DebtInstrumentInterestRateIncreaseFromFailureToMaintainInvestmentRating
Debt Instrument, Interest Rate, Increase From Failure to Maintain Investment Rating
Pertains to the term of the agreement.
hrzn_DebtInstrumentConvertibleMaximumBeneficialOwnershipPercentage
Debt Instrument, Convertible, Maximum Beneficial Ownership Percentage
Information pertaining to the agreement.
Momentum US Bidco LLC [Member]
Pertains to Momentum US Bidco LLC.
E La Carte, Inc [Member]
Represents E La Carte, Inc.
Lemongrass Holdings, Inc [Member]
Represents Lemongrass Holdings, Inc.
Supply Network Visiblity Holdings LLC [Member]
Represents Supply Network Visiblity Holdings LLC.
Base management fee (Note 3)
Management Fee Expense
us-gaap_IncentiveFeeExpense
Incentive Fee Expense
us-gaap_RestrictedCashEquivalents
Restricted investments in money market funds
Administrative fee (Note 3)
Administrative Fees Expense
General and administrative
Preferred Stock Warrants [Member]
Represents Preferred Stock Warrants.
Cash
Mustang Bio, Inc [Member]
Represents Mustang Bio, Inc.
Common Stock Warrants [Member]
Represents Common Stock Warrants.
AccuVein Inc [Member]
Represents AccuVein Inc.
Aerin Medical, Inc [Member]
Represents Aerin Medical, Inc.
Investments in money market funds
Xeris Pharmaceuticals, Inc [Member]
Represents Xeris Pharmaceuticals, Inc.
CVRx, Inc [Member]
Represents CVRx, Inc.
Amendment Flag
City Area Code
Use of Estimates, Policy [Policy Text Block]
New Accounting Pronouncements, Policy [Policy Text Block]
PebblePost, Inc [Member]
Represents PebblePost, Inc.
Caastle, Inc [Member]
Represents Caastle, Inc.
Getaround, Inc [Member]
Represents Getaround, Inc.
Meditrina, Inc [Member]
Represents Meditrina, Inc
VERO Biotech LLC [Member]
Represents VERO Biotech LLC.
LiquiGlide, Inc [Member]
Represents LiquiGlide, Inc.
Intelepeer Holdings, Inc [Member]
Represents Intelepeer Holdings, Inc.
Silk, Inc [Member]
Represents Silk, Inc.
Global Worldwide LLC [Member]
Represents Global Worldwide LLC.
Rocket Lawyer Incorporated [Member]
Represents Rocket Lawyer Incorporated.
Current Fiscal Year End Date
Skillshare, Inc [Member]
Represents Skillshare, Inc.
Quip NYC Inc [Member]
Represents Quip NYC Inc.
Updater, Inc [Member]
Represents Updater, Inc.
CPG Beyond, Inc [Member]
Represents CPG Beyond, Inc.
Revinate Holdings, Inc [Member]
Represents Revinate Holdings, Inc.
Interest receivable
Document Fiscal Period Focus
SIGNiX, Inc [Member]
Represents SIGNiX, Inc.
Document Fiscal Year Focus
Consolidation, Policy [Policy Text Block]
Avalanche Technology, Inc [Member]
Represents Avalanche Technology, Inc.
Document Period End Date
Lotame Solutions, Inc. [Member]
Represents Lotame Solutions, Inc.
Entity File Number
Kate Farms, Inc [Member]
Represents Kate Farms, Inc.
Entity Emerging Growth Company
Document Type
Net realized loss on extinguishment of debt
Gain (Loss) on Extinguishment of Debt
Net realized loss on extinguishment of debt
Medsphere Systems Corporation [Member]
Represents Medsphere Systems Corporation.
Investments at cost
Topia Mobility, Inc [Member]
Represents Topia Mobility, Inc.
Entity Small Business
xAd, Inc [Member]
Represents xAd, Inc.
Entity Shell Company
Royalty Agreement [Member]
Represents royalty agreement.
U S Bank Money Market Deposit Account [Member]
Represents US bank money market deposit account.
Document Information [Line Items]
Unrestricted Short Term Investments [Member]
Represents unrestricted short term investments.
Document Information [Table]
NAV %
Restricted Short Term Investments [Member]
Represents restricted short term investments.
Entity Public Float
SnagAJob.com, Inc [Member]
Represents SnagAJob.com, Inc.
Entity Filer Category
Number of Shares (in shares)
Entity Current Reporting Status
Entity Voluntary Filers
Principal Amount
Entity Well-known Seasoned Issuer
Award Timing MNPI Disclosure [Text Block]
us-gaap_ConcentrationRiskPercentage1
Concentration Risk, Percentage
ecd_AwardTmgMnpiCnsdrdFlag
Award Timing MNPI Considered [Flag]
Entity Tax Identification Number
Entity Central Index Key
Insider Trading Policies and Procedures [Line Items]
Entity Registrant Name
ecd_InsiderTrdPoliciesProcAdoptedFlag
Insider Trading Policies and Procedures Adopted [Flag]
Entity [Domain]
Legal Entity [Axis]
Entity Address, Address Line One
ecd_NonRule10b51ArrTrmntdFlag
Non-Rule 10b5-1 Arrangement Terminated [Flag]
Entity Address, City or Town
ecd_Rule10b51ArrTrmntdFlag
Rule 10b5-1 Arrangement Terminated [Flag]
ecd_Rule10b51ArrAdoptedFlag
Rule 10b5-1 Arrangement Adopted [Flag]
Entity Address, Postal Zip Code
Entity Address, State or Province
Concentration Risk Type [Axis]
ecd_NonRule10b51ArrAdoptedFlag
Non-Rule 10b5-1 Arrangement Adopted [Flag]
Concentration Risk Type [Domain]
Material Terms of Trading Arrangement [Text Block]
Entity Common Stock, Shares Outstanding
Schedule of Investments [Text Block]
Trading Arrangements, by Individual [Table]
Investment Holdings, Schedule of Investments [Table Text Block]
Total return based on a market value
us-gaap_InvestmentCompanyTotalReturn
Hometeam Technologies, Inc [Member]
Represents Hometeam Technologies, Inc.
Net investment income with incentive fees (5)
us-gaap_InvestmentCompanyInvestmentIncomeLossRatioAfterIncentiveAllocation
Professional fees
Incentive fees
us-gaap_InvestmentCompanyIncentiveFeeToAverageNetAssets
Investments [Domain]
Trading Symbol
Nature of Operation, Product Information, Concentration of Risk [Table]
Expenses without incentive fees (4)
Concentration Risk Benchmark [Axis]
Net expenses
us-gaap_InvestmentCompanyExpenseRatioIncludingIncentiveFee
Investment Holdings [Table]
Concentration Risk Benchmark [Domain]
Investment Type [Axis]
Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block]
Net asset value per common share (in dollars per share)
Net asset value at beginning of period (in dollars per share)
Net asset value at end of period (in dollars per share)
Sparkcharge, Inc. [Member]
Represents information pertaining to Sparkcharge, inc.
Return of capital (in dollars per share)
us-gaap_InvestmentCompanyTaxReturnOfCapitalDistributionPerShare
Local Phone Number
Net (decrease) increase in net assets resulting from operations (in dollars per share)
Net decrease in net assets resulting from operations per common share - basic (in dollars per share)
Realized loss on investments (in dollars per share)
us-gaap_InvestmentCompanyGainLossOnInvestmentPerShare
us-gaap_TableTextBlock
Notes Tables
Net investment income (in dollars per share)
Net investment income per common share - basic (in dollars per share)
us-gaap_InvestmentCompanyDistributionToShareholdersPerShare
Distributions declared (in dollars per share)
Investment Company, Financial Highlights [Table]
Investment Company, Financial Highlights [Text Block]
Investment Company, Financial Highlights [Table Text Block]
Purchases
us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossReductions
Reductions
us-gaap_GainLossOnSaleOfInvestments
Net realized loss on investments
Interest Income, Net
The amount of interest income, net.
Long Grove Pharmaceuticals, LLC [Member]
Related to Long Grove Pharmaceuticals, LLC
MML US, Inc [Member]
Related to MML US, Inc.
Investments in and Advances to Affiliates [Table Text Block]
Investments in and Advances to Affiliates [Table]
SafelyYou, Inc [Member]
Related to SafelyYou, Inc.
Nexii Building Solutions, Inc [Member]
Related to Nexii Building Solutions, Inc.
us-gaap_TaxBasisOfInvestmentsCostForIncomeTaxPurposes
Investment, Tax Basis, Cost
Investment Holdings [Text Block]
Related Party Transaction [Axis]
Related Party Transaction [Domain]
us-gaap_TaxBasisOfInvestmentsGrossUnrealizedAppreciation
Investment, Tax Basis, Unrealized Gain
us-gaap_TaxBasisOfInvestmentsGrossUnrealizedDepreciation
Investment, Tax Basis, Unrealized Loss
Supply Network Visibility Holdings, LLC [Member]
Related to Supply Network Visibility Holdings, LLC.
Federal Income Tax Note [Table Text Block]
Federal Income Tax Note [Table]
Three Year I Curve [Member]
Related to the Three Year I Curve.
Interest expense
Schedule of Investments [Table]
Amortization of debt issuance costs
Amortization of Debt Issuance Costs
us-gaap_DisclosureTextBlockAbstract
Notes to Financial Statements
Subsequent Event [Member]
Subsequent Event [Table]
Subsequent Event Type [Axis]
Subsequent Event Type [Domain]
Subsequent Events [Text Block]
Fair Value Measurement, Policy [Policy Text Block]
Distributions payable
Segment Reporting, Policy [Policy Text Block]
Income Tax, Policy [Policy Text Block]
Fee income
Average net asset value
hrzn_AverageNetAssets
Amount of average net assets (liabilities).
Common Stock Outstanding [Member]
Represents common stock outstanding.
us-gaap_SharesIssuedPricePerShare
Shares Issued, Price Per Share (in dollars per share)
Software, Healthcare Information and Service [Member]
Represents software for healthcare information and service.
Equity [Text Block]
Stockholders' Equity, Policy [Policy Text Block]
Decrease in base management fee payable
Decrease in incentive fee payable
us-gaap_IncentiveFeePayable
Incentive Fee Payable
Investment income
Debt, Policy [Policy Text Block]
Investment, Affiliated Issuer, Controlled [Member]
Viken Detection Corporation [Member]
Represents Viken Detection Corporation.
Payment-in-kind (“PIK”) interest income
Interest Income, Operating, Paid in Kind
PIK interest on investments
hrzn_AdministrativeFeesPayable
Administrative Fees Payable
Amount of payable for administrative fees.
Investment, Affiliated Issuer, Noncontrolled [Member]
Four Investments [Member]
Represents four investments.
December 31, 2026 Expiration [Member]
Represents information pertaining to the expiration of the total contingent future liability.
BioVaxys Technology Corp. [Member]
Represents BioVaxys Technology Corp.
Assets of Powerscourt Investments XXV, LP [Member]
Represents assets of Powerscourt Investments XXV, LP.
hrzn_StockRepurchaseProgramMaximumPercentageOfNetAssetValue
Stock Repurchase Program, Maximum Percentage of Net Asset Value
Maximum percentage of net asset value for repurchase of stock under the program.
Interest (reversal) income
hrzn_StockRepurchaseProgramPercentageOfOutstandingStockMaximum
Stock Repurchase Program, Percentage of Outstanding Stock Maximum
Maximum number of shares that may be repurchased in accordance with the plan as a proportion of outstanding capital stock.
us-gaap_NetInvestmentIncome
Net investment income before excise tax
us-gaap_InvestmentCompanyIssuanceOfSharesPerShare
Net dilution from issuance of common stock (in dollars per share)
Parse Biosciences, Inc. [Member]
Represents Parse Biosciences, Inc.
MicroTransponder, Inc. [Member]
Represents MicroTransponder, Inc.
Net accretion from repurchase of common stock (in dollars per share)
Everstream Holdings, LLC [Member]
Represents Everstream Holdings LLC.
us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents
Total cash, cash equivalents and restricted cash
us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations
Beginning of period
End of period
Assets
hrzn_InvestmentCompanyRetainedEarningsAccumulatedDeficit
Total
Amount of accumulated undistributed earnings (deficit).
Interest income
us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect
Net increase in cash, cash equivalents and restricted cash
The 2019 Notes [Member]
Related to the 2019 notes.
Transfers and Servicing of Financial Assets, Servicing of Financial Assets, Policy [Policy Text Block]
Cash, cash equivalents and restricted cash:
Investment, Identifier [Axis]
us-gaap_NetCashProvidedByUsedInFinancingActivities
Net cash (used in) provided by financing activities
hrzn_InvestmentIncomeAttributableToNoncashPaidinkindInterestPercent
Investment, Income Attributable to Non-cash Paid-in-Kind Interest, Percent
The percent of investment income attributable to non-cash PIK interest.
Sale of Stock [Axis]
Cash Rate
Sale of Stock [Domain]
Floor
us-gaap_InvestmentIncomeOperatingAfterExpenseAndTax
Net investment income
Net investment income, net of excise tax
us-gaap_NetCashProvidedByUsedInOperatingActivities
Net cash provided by (used in) operating activities
Provision for excise tax
Investment, Issuer Name [Domain]
Investment, Issuer Name [Axis]
Investment, Issuer Affiliation [Axis]
Investment, Issuer Affiliation [Domain]
Conversion of 2031 Notes Into Common Stock [Member]
Represents the conversion of the 2031 notes into common stock.
us-gaap_ExciseAndSalesTaxes
Excise and Sales Taxes
Investment, Policy [Policy Text Block]
Investment, Unaffiliated Issuer [Member]
us-gaap_PaymentsOfStockIssuanceCosts
Payments of Stock Issuance Costs
us-gaap_PaymentsOfDividends
Distributions paid
us-gaap_CostsAndExpenses
Total expenses
Expenses
Scenario [Domain]
Forecast [Member]
Proceeds from issuance of common stock, net of offering costs
Proceeds from Issuance of Common Stock
Scenario [Axis]
Management Service, Incentive [Member]
Unfunded Loan Commitment [Member]
us-gaap_PaymentsOfFinancingCosts
Debt issuance costs
ICFR Auditor Attestation Flag
us-gaap_UnrecognizedTaxBenefits
Unrecognized Tax Benefits, Ending Balance
Accounting Policies [Abstract]
us-gaap_OpenTaxYear
Open Tax Year
Concentration Risk Disclosure [Text Block]
us-gaap_RealizedGainLossInvestmentAndDerivativeOperatingAfterTax
Net realized loss on investments
Concentration Risk [Table]
Distributions declared per share (in dollars per share)
us-gaap_CommonStockDividendsPerShareCashPaid
Common Stock, Dividends, Per Share, Cash Paid (in dollars per share)
Debt Securities [Member]
Proceeds from Convertible Debt
Proceeds from Convertible Debt
Auditor Name
Auditor Firm ID
Auditor Location
us-gaap_RepaymentsOfNotesPayable
Repayment of note
us-gaap_SharePrice
Share Price (in dollars per share)
Per share market value, beginning of period (in dollars per share)
Per share market value, end of period (in dollars per share)
us-gaap_RepaymentsOfLinesOfCredit
Repayment of Credit Facilities
Weighted average shares outstanding - diluted (in shares)
Proceeds from issuance of 2028 Notes
us-gaap_OperatingLossCarryforwards
Operating Loss Carryforwards
Advances on Credit Facilities
Statement of Financial Position [Abstract]
Loss per common share - diluted (in dollars per share)
us-gaap_WeightedAverageNumberOfSharesOutstandingBasic
Denominator for basic weighted average shares (in shares)
us-gaap_EarningsPerShareBasic
Loss per common share - basic (in dollars per share)
Statement of Cash Flows [Abstract]
Statement of Stockholders' Equity [Abstract]
Asset Acquisition [Axis]
September 30, 2028 Expiration [Member]
Represents information pertaining to the September 30, 2028 expiration.
us-gaap_AssetAcquisitionConsiderationTransferred
Asset Acquisition, Consideration Transferred
srt_StockRepurchaseProgramAuthorizedAmount1
Share Repurchase Program, Authorized, Amount
Equity received in settlement of interest and fee income
Amount of equity received in settlement of interest and fee income.
The 2030 Convertible Notes [Member]
Represents information pertaining to the 2030 Convertible Notes.
Fair Value, Assets Measured on Recurring Basis [Table Text Block]
Payment date
Dividends Declared [Table Text Block]
Cash flows from financing activities:
Shengrow Inc. [Member]
Represents information pertaining to Shengrow Inc.
Asset Acquisition [Domain]
Record date
us-gaap_DividendsPayableCurrentAndNoncurrent
Distributions payable
us-gaap_DividendsPayableAmountPerShare
Dividends Payable, Amount Per Share (in dollars per share)
Dividends [Axis]
Dividends [Domain]
Involuntary Liquidation Preference (in dollars per share)
hrzn_DebtInstrumentConvertibleAcceleratedUnamortizedDebtIssuanceCosts
Debt Instrument, Convertible, Accelerated Unamortized Debt Issuance Costs
The accelerated unamortized debt issuance costs for convertible debt instruments.
hrzn_DebtInstrumentConvertibleWeightedAverageConversionPrice
Debt Instrument, Convertible, Weighted Average Conversion Price (in dollars per share)
The weighted average conversion price for convertible debt instruments.
Conversion of 2030 Notes Into Common Stock [Member]
Represents information pertaining to the conversion of 2030 notes into common stock.
Dividends Payable [Table]
Class of Stock [Axis]
Class of Stock [Domain]
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]
Hound Labs II, LLC [Member]
Represents information pertaining to Hound Labs II, LLC (New Hound).
Apkudo, Inc. [Member]
Represents information pertaining to Apkudo, Inc.
Income Tax Disclosure [Text Block]
us-gaap_AccumulatedAmortizationDeferredFinanceCosts
Accumulated Amortization, Debt Issuance Costs
Schedule of Debt [Table Text Block]
Shengrow, Inc. aka Soli Organic, Inc. [Member]
Represents information pertaining to Shengrow, Inc. aka Soli Organic, Inc.
March 31, 2026 Expiration [Member]
Represents information pertaining to the expiration of the total contingent future liability.
December 31, 2025 Expiration [Member]
Represents information pertaining to the expiration of the total contingent future liability.
June 30, 2026 Expiration [Member]
Represents information pertaining to the expiration of the total contingent future liability.
us-gaap_PaymentsToAcquireInvestments
Payments to Acquire Investments
Revolver Loan, Prime Index, One [Member]
Represents information pertaining to the first revolver loans' prime index.
hrzn_BaseManagementAndIncentiveFeesAmountWaivedPerQuarter
Base Management and Incentive Fees, Amount Waived per Quarter
The amount of base management and incentive fees waived per quarter.
Merger Agreement Fee Waiver [Member]
Represents information pertaining to the merger agreement with a fee waiver.
Adjustment for dilutive effect of Convertible Notes (1) (in shares)
Incremental Common Shares Attributable to Dilutive Effect of Conversion of Debt Securities (in shares)
Tallac Therapeutics, Inc [Member]
Represents Tallac Therapeutics, Inc.
Supplemental non-cash operating and financing activities:
us-gaap_FairValueOfAssetsAcquired
Fair Value of Assets Acquired
Weighted average shares outstanding - basic (in shares)
Supplemental disclosure of cash flow information:
Maturity Date
Numerator for decrease in net assets per share
Numerator for basic earnings per share
Performance based incentive fee (Note 3)
Amount of performance based incentive fee.
hrzn_InvestmentCompanyInvestmentIncomeNet
Total investment income
Amount of investment income, net of investment expense for investment company.
Investment [Table Text Block]
us-gaap_NetIncomeLossAvailableToCommonStockholdersDiluted
Numerator for diluted earnings per share
Net realized (loss) gain on investments
hrzn_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetRealizedGainLossIncludedInEarnings
Amount of realized gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3).
Adjustment for interest expense and debt issuance costs on Convertible Notes (1)
Unrealized appreciation (depreciation) included in earnings
Amount of unrealized appreciation (depreciation) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3).
hrzn_InvestmentsNonaccrualInterestIncome
Investments, Nonaccrual, Interest Income
Amount of interest income on investment, on nonaccrual status.
hrzn_AdjustmentsToAdditionalPaidInCapitalNondeductibleExciseTaxesPaid
Adjustments to Additional Paid in Capital, Non-deductible Excise Taxes Paid
Amount of increase to additional paid in capital for non-deductible excise taxes paid.
hrzn_LiabilitiesAndNetAssets
Total liabilities and net assets
Amount of liabilities and net assets.
Net decrease in net assets resulting from operations
Net decrease in net assets resulting from operations
Net decrease in net assets resulting from operations
Transfer out of debt investments
Amount of transfer of financial instrument classified as an asset between investments.
BrightInsight, Inc. [Member]
Represents BrightInsight, Inc.
Optoro, Inc. [Member]
Represents Optoro, Inc.
PDS Biotechnology Corporation [Member]
Represents PDS Biotechnology Corporation.
Warrant [Member]
Slingshot Aerospace, Inc. [Member]
Represents Slingshot Aerospace, Inc.
Robin Healthcare, Inc. [Member]
Represents Robin Healthcare, Inc.
Evelo Biosciences, Inc. [Member]
Represents Evelo Biosciences, Inc..
us-gaap_EarningsPerShareBasicUndistributed
Earnings Per Share, Basic, Undistributed (in dollars per share)
Earnings Per Share, Basic, by Common Class, Including Two-Class Method [Table]
Earnings Per Share [Text Block]
Related Party Transaction [Table]
Related Party Transactions Disclosure [Text Block]
Increase (decrease) in other accrued expenses
Schedule of Related Party Transactions [Table Text Block]
Warrants received in settlement of fee income
Amount of warrants received in settlement of fee income.
Asset-backed Notes 2022 [Member]
Represents 2022 asset-backed notes.
Reclassification of permanent tax differences (Note 2)
Amount of reclassification of permanent tax differences.
us-gaap_DebtInstrumentRedemptionPricePercentage
Debt Instrument, Redemption Price, Percentage
Asset-backed Notes 2019 [Member]
Represents 2019 asset-backed notes.
Refinanced debt investment balances
Amount of refinanced debt investment balances in noncash transaction.
hrzn_IncentiveFeeCapAndDeferralMechanismReductionToExpense
Incentive Fee Cap and Deferral Mechanism Reduction to Expense
Amount of inventive fee cap and deferral mechanism reduction to expense.
Net realized and unrealized loss
Unused commitment
us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrency
Net realized and unrealized loss
us-gaap_InvestmentCompanyVoluntaryFeeWaived
Investment Company, Voluntary Fee Waived
us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1
Debt Instrument, Convertible, Threshold Consecutive Trading Days
us-gaap_DebtInstrumentConvertibleConversionPrice1
Debt Instrument, Convertible, Conversion Price (in dollars per share)
us-gaap_InvestmentCompanyDistributableEarningsLossAccumulatedCapitalLossCarryforward
Long term capital loss carry forward
us-gaap_DebtInstrumentConvertibleStockPriceTrigger
Debt Instrument, Convertible, Stock Price Trigger (in dollars per share)
Net expenses
hrzn_InvestmentCompanyExpenseRatioExcludingVoluntaryFeeWaiver
Percentage, before deduction of fee waiver, of expense to average net assets.
us-gaap_DebtInstrumentConvertibleNumberOfEquityInstruments
Debt Instrument, Convertible, Number of Equity Instruments
us-gaap_InvestmentCompanyDistributableEarningsLossAccumulatedOrdinaryIncomeLoss
Undistributed ordinary income
Tigo Energy, Inc. [Member]
Represents Tigo Energy, Inc.
Havenly, Inc. [Member]
Represents Havenly, Inc.
Incentive fees
hrzn_InvestmentCompanyIncentiveFeeToAverageNetAssetsExcludingVoluntaryFeeWaiver
Percentage, before deduction of voluntary fee waiver, of incentive fee expense to average net assets.
Expenses without incentive fees
Percentage, before deduction of voluntary fee waiver and before deduction of incentive fee, of expense to average net assets.
us-gaap_InvestmentCompanyDividendDistribution
Distributions declared
Net investment income with incentive fees
Net investment income with incentive fees
Percentage, before deduction of voluntary fee waiver and after incentive allocation, of investment income (loss) to average net assets.
The 2022-1 Securitization [Member]
Represents the 2022-1 Securitization.
us-gaap_DebtInstrumentMaturityDate
Debt Instrument, Maturity Date
us-gaap_SharesOutstanding
Balance (in shares)
Balance (in shares)
Shares outstanding at end of period (in shares)
Common stock, shares outstanding (in shares)
us-gaap_LongTermDebtWeightedAverageInterestRateOverTime
Long-Term Debt, Weighted Average Interest Rate, over Time
Preferred stock, shares oustanding (in shares)
us-gaap_IncreaseDecreaseInOtherOperatingAssets
Increase in other assets
us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Debt Instrument, Basis Spread on Variable Rate
us-gaap_DebtInstrumentInterestRateStatedPercentage
Debt Instrument, Interest Rate, Stated Percentage
us-gaap_DebtInstrumentFairValue
Debt Instrument, Fair Value Disclosure
Total commitment
Debt Instrument, Face Amount
Dividends, stock
Dividends, cash
Debt Instrument [Axis]
Debt Instrument, Name [Domain]
The 6.25% Notes due 2027 [Member]
Represents the 6.25% Notes due 2027.
us-gaap_IncreaseDecreaseInAccruedInterestReceivableNet
Decrease (increase) in interest receivable
Alternative Energy [Member]
Variable Rate [Domain]
Prime Rate [Member]
Schedule of Long-Term Debt Instruments [Table Text Block]
Schedule of Long-Term Debt Instruments [Table]
Variable Rate [Axis]
Kodiak Robotics, Inc. [Member]
Represents Kodiak Robotics, Inc.
Transfer out of Level 3
us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
Balance
Balance
us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3
us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOutOfLevel3
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3
us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
Purchase of investments
us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
Proceeds from sale of investments
us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements
Principal payments received on investments
us-gaap_StockRepurchasedDuringPeriodShares
Stock Repurchased During Period, Shares (in shares)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table]
us-gaap_StockRepurchasedDuringPeriodValue
Stock Repurchased During Period, Value
Imunon, Inc [Member]
Represents Imunon, Inc.
Issuance of common stock under dividend reinvestment plan
Issuance of common stock under dividend reinvestment plan (in shares)
Lumithera, Inc. [Member]
Represents Lumithera, Inc.
Dividends, shares (in shares)
Issuance of common stock in extinguishment of debt
Issuance of common stock in extinguishment of debt (in shares)
us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd
Line of Credit Facility, Interest Rate at Period End
us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Line of Credit Facility, Remaining Borrowing Capacity
us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Line of Credit Facility, Maximum Borrowing Capacity
us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity
Line of Credit Facility, Current Borrowing Capacity
us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage
Related and Nonrelated Parties [Axis]
Related and Nonrelated Parties [Domain]
us-gaap_LineOfCreditFacilityFairValueOfAmountOutstanding
Line of Credit Facility, Fair Value of Amount Outstanding
Ceiling
The ceiling rate of the investment owned.
Energy Efficiency [Member]
Represents Energy Efficiency.
Collaborative Arrangement and Arrangement Other than Collaborative [Domain]
Issuance of common stock, net of offering costs (in shares)
Stock Issued During Period, Shares, New Issues (in shares)
ETP
The end of term payment rate (ETP) on investment owned.
Reported Value Measurement [Member]
Issuance of common stock, net of offering costs
Term Loan, Prime Index, Four [Member]
Represents term loan with prime index.
Distributable loss
Term Loan, Prime Index, Five [Member]
Represents term loan with prime index.
Term Loan, Prime Index, Two [Member]
Represents term loan with prime index.
Measurement Input, Discount Rate [Member]
Term Loan, Prime Index, Three [Member]
Represents term loan with prime index.
Measurement Input, Share Price [Member]
Debt Disclosure [Text Block]
Measurement Input, Price Volatility [Member]
Term Loan, Prime Index, Six [Member]
Represents term loan with prime index.
Changes in assets and liabilities:
Term Loan, Prime Index, Seven [Member]
Represents term loan with prime index.
Measurement Input, Discount for Lack of Marketability [Member]
Accrued interest converted to common stock
us-gaap_DebtInstrumentMeasurementInput
Debt Instrument, Measurement Input
Measurement Input Type [Axis]
Measurement Input Type [Domain]
Net unrealized appreciation (depreciation) on investments
Net unrealized appreciation (depreciation) on investments
Unrealized Gain (Loss) on Investments
Net unrealized (appreciation) depreciation on investments
Valuation Technique, Discounted Cash Flow [Member]
Valuation Approach and Technique [Axis]
Valuation Approach and Technique [Domain]
us-gaap_DebtConversionConvertedInstrumentSharesIssued1
Debt Conversion, Converted Instrument, Shares Issued (in shares)
Debt converted to common stock
Debt Conversion, Original Debt, Amount
Debt Conversion Description [Axis]
Debt Conversion, Name [Domain]
Non-cash income
Horizon Technology Finance Management LLC (the Advisor) [Member]
Represents Horizon Technology Finance Management LLC (the “Advisor”).
hrzn_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPaymentInkindInterest
PIK interest on investments
Amount of payment in-king interest on financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.
Cadrenal Therapeutics, Inc. [Member]
Represents Cadrenal Therapeutics, Inc.
Affiliated Entity [Member]
Investments, fair value
Other book-tax differences
hrzn_OtherBooktaxDifferences
Amount of other book-tax differences.
Net realized gain (loss) on investments
Net realized gain (loss)
hrzn_InvestmentCompanyDistributableEarningsLossAccumulatedDepreciation
Unrealized depreciation
Amount of accumulated undistributed deficit from unrealized depreciation of investment company.
From net investment income (in dollars per share)
hrzn_InvestmentCompanyDistributionToShareholdersPerShareNetInvestmentIncome
Per share or unit amount of distribution from net investment income to shareholders.
hrzn_InvestmentCompanyDistributableEarningsLossAccumulatedOtherTemporaryDifferences
Other temporary differences
Amount of accumulated undistributed earnings (deficit) from other temporary differences of investment company.
From net realized gain on investments (in dollars per share)
hrzn_InvestmentCompanyDistributionToShareholdersPerShareNetRealizedGainOnInvestments
Per share or unit amount of distribution from net realized gain on investments to shareholders.
Schedule of Investment Company, Distributable Earnings (Loss) [Table Text Block]
Tabular disclosure of accumulated undistributed tax basis earnings (deficit).
Other (in dollars per share)
hrzn_InvestmentCompanyDistributionToShareholdersPerShareOther
Per share or unit amount of distribution from other sources not separately classified to shareholders.
Change in capital loss carry forward
hrzn_CapitalLossCarryforwardIncreaseDecrease
Amount of increase (decrease) in capital loss carryforward.
Schedule of Tax Characters of Distribution Paid [Table Text Block]
Tabular disclosure of tax characters of distribution paid.
hrzn_InvestmentCompanyTotalDistribution
Total
Amount of total distribution.
Fair Value Measurement Inputs and Valuation Techniques [Table]
hrzn_InvestmentCompanyDistributableEarningsLossAccumulatedAppreciation
Unrealized appreciation
Amount of accumulated undistributed earnings (deficit) from unrealized appreciation of investment company.
Unrealized appreciation (depreciation) on investments (in dollars per share)
Per share or unit amount, after investment expense, of (depreciation) appreciation.
hrzn_TaxableIncomeBeforeDeductionsForDistributions
Taxable income before deductions for distributions
Amount of taxable income before deductions for distributions.
Fair Value Measurement Inputs and Valuation Techniques [Table Text Block]
Common stock, par value $0.001 per share, 100,000,000 shares authorized, 45,781,280 and 40,043,312 shares issued and 45,613,815 and 39,875,847 shares outstanding as of December 31, 2025 and 2024, respectively
Investments at fair value
Investments, fair value
Investments, fair value
Fair Value, Recurring and Nonrecurring [Table]
Measurement Frequency [Axis]
Adjustments to reconcile net decrease in net assets resulting from operations to net cash provided by (used in) operating activities:
Measurement Frequency [Domain]
Average debt per share (in dollars per share)
hrzn_InvestmentCompanyAverageDebtPerShare
The average debt per share in investment company.
Credit Facilities [Member]
Represents the credit facilities.
Fair Value, Recurring [Member]
Portfolio turnover ratio
hrzn_InvestmentCompanyPortfolioTurnoverRatio
The portfolio turnover ratio for investment company.
The 2019-1 Securitization [Member]
Represents 2019-1 Securitization.
Common stock, shares authorized (in shares)
Common stock, shares issued (in shares)
Common stock, par value (in dollars per share)
Average market value per unit (in dollars per share)
Per share average market value of debt instrument.
Asset Coverage Per Unit (in dollars per share)
Per share asset coverage of debt instrument.
Statistical Measurement [Domain]
Maximum [Member]
Minimum [Member]
us-gaap_PaymentsForPurchaseOfSecuritiesOperatingActivities
Purchase of investments
Weighted Average [Member]
Ownership [Domain]
Statistical Measurement [Axis]
Term Loan, Prime Index, Eight [Member]
Represents term loan with prime index.
Ownership [Axis]
Preferred stock, par value $0.001 per share, 1,000,000 shares authorized, zero shares issued and outstanding as of December 31, 2025 and 2024
Preferred stock, shares issued (in shares)
Net assets at the end of the period
hrzn_NetAssets
Total net assets
Amount of net assets (liabilities).
Cash paid for interest
Preferred stock, shares authorized (in shares)
Portion at Fair Value Measurement [Member]
Preferred stock, par value (in dollars per share)
Estimate of Fair Value Measurement [Member]
hrzn_InvestmentCompanyDividendDistributionPaid
Ordinary income
Amount of dividend distribution from ordinary income and capital gain paid during the period. Excludes distribution for tax return of capital.
Measurement Basis [Axis]
Fair Value, Inputs, Level 3 [Member]
Proceeds from sale of investments
Principal payments received on investments
hrzn_TaxableEarningsPerShareBasic
Taxable Earnings Per Share, Basic (in dollars per share)
The amount of taxable net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.
Fair Value Hierarchy and NAV [Domain]
HIMV LLC [Member]
Fair Value, Inputs, Level 1 [Member]
Fair Value, Inputs, Level 2 [Member]
Fair Value Hierarchy and NAV [Axis]
September 30, 2026 Expiration [Member]
Represents information pertaining to the expiration of the total contingent future liability.
Horizon Technology Finance Corporation [Member]
Information by consolidated entity or group of entities.
Co-lender [Member]
Information pertaining to the co-lender.
Aulea Medical, Inc. [Member]
Represents Aulea Medical, Inc
Debt Investments [Member]
Related to debt investments.
Investment Concentration Risk [Member]
Related to investment concentration risk.
Cash flows from operating activities:
Ceribell, Inc. [Member]
Related to Ceribell, Inc.
Cognoa, Inc. [Member]
Related to Cognoa, Inc.
Divergent Technologies, Inc. [Member]
Related to Divergent Technologies, Inc.
DropOff, Inc. [Member]
Related to DropOff, Inc.
Statement [Line Items]
Better Place Forests Co. [Member]
Related to Better Place Forests Co.
Britecore Holdings, Inc. [Member]
Related to Britecore Holdings, Inc.
Canary Medical Inc. [Member]
Related to Canary Medical Inc.
Paid-in capital in excess of par
KSQ Therapeutics, Inc. [Member]
Related to KSQ Therapeutics, Inc.
Unfunded commitments, principal balance
us-gaap_FairValueDisclosureOffbalanceSheetRisksFaceAmountLiability
Native Microbials, Inc. [Member]
Related to Native Microbials, Inc.
Scientia Vascular, Inc. [Member]
Related to Scientia Vascular, Inc.
Hound Labs, Inc. [Member]
Related to Hound Labs, Inc.
Fair value of unfunded commitment liability
us-gaap_FairValueDisclosureOffbalanceSheetRisksAmountLiability
Fair Value Disclosure, off-Balance-Sheet Risks, Amount, Liability
Key Facility [Member]
Related to Key Facility.
Net assets
NYL Facility [Member]
Related to NYL Facility.
The 2027 Notes [Member]
Related to the 2027 notes.
Sonex Health, Inc. [Member]
Related to Sonex Health, Inc.
Stealth BioTherapeutics Inc. [Member]
Related to Stealth BioTherapeutics Inc.
Swift Health Systems Inc. [Member]
Related to Swift Health Systems Inc.
Fair Value, by Balance Sheet Grouping [Table]
The 2026 Notes [Member]
Related to the 2026 notes.
Elligo Healthcare Research, Inc. [Member]
Represent Elligo Healthcare Research, Inc
Fair Value Disclosures [Text Block]
Mirantis, Inc [Member]
Represents Mirantis, Inc.
hrzn_LineOfCreditFacilityMaximumBorrowingCapacityAccordianFeature
Line of Credit Facility, Maximum Borrowing Capacity, Accordian Feature
Maximum borrowing capacity under the credit facility after the accordion feature increase.
hrzn_LineOfCreditFacilityAdvanceRateOfEligibleDebtInvestments
Line of Credit Facility, Advance Rate of Eligible Debt Investments
The advance rate of eligible debt investments under line of credit facility.
hrzn_AssetCoverageToBorrowingsRatioPercent
Asset Coverage to Borrowings, Ratio, Percent
The asset coverage to borrowings ratio percentage.
us-gaap_Liabilities
Total liabilities
Commitments and contingencies (Notes 3 and 8)
Noodle Partners, Inc. [Member]
Represents Noodle Partners, Inc.
hrzn_DebtInstrumentVariableRate
Debt Instrument, Variable Rate
The variable rate of debt instrument.
The 2022 Notes [Member]
Related to the 2022 notes.
O 2025 M4 1 Dividends [Member]
Information regarding distributions.
O 2025 M4 2 Dividends [Member]
Information regarding distributions.
Term Loan, Fixed Index Three [Member]
Represents term loan with fixed index.
Term Loan, Fixed Index Two [Member]
Represents term loan with fixed index.
Candesant Biomedical, Inc. [Member]
Represents Candesant Biomedical, Inc.
us-gaap_SalesAndExciseTaxPayableCurrentAndNoncurrent
Sales and Excise Tax Payable
O 2025 M4 3 Dividends [Member]
Information regarding distributions.
Consolidated Entities [Axis]
Term Loan, Fixed Index One [Member]
Represents term loan with fixed index.
Consolidated Entities [Domain]
The 2023 Equity Distribution Agreement [Member]
Represents the 2023 Equity Distribution Agreement.
Other accrued expenses
hrzn_RealizedInvestmentGainsLossesNetOfDebtExtinguishment
Net realized loss
Amount of realized gain (loss) on investment, net of debt extinguishment.
MasteryPrep, LLC [Member]
Represents information pertaining to MasteryPrep, LLC
June 30, 2028 Expiration [Member]
Represents information pertaining to the expiration of the total contingent future liability.
Retained Earnings [Member]
us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1
Share Repurchase Program, Remaining Authorized, Amount
Alternative Energy Sector [Member]
Represents information pertaining to the alternative energy sector.
Additional Paid-in Capital [Member]
Common Stock [Member]
Preferred Stock [Member]
hrzn_RealizedGainlossExtinguishmentOfDebt
Net realized loss on extinguishment of debt
The amount of realized gain or loss from the extinguishment of debt.
Equity Components [Axis]
hrzn_PolicyTable
Equity Component [Domain]
Other Investments [Member]
Elligo Health Research, Inc [Member]
Represents Elligo Health Research, Inc.
Total borrowings outstanding, net
Borrowings (Note 7)
New Aerofarms, Inc. assignee of Aerofarms, Inc [Member]
Represents New Aerofarms, Inc. assignee of Aerofarms, Inc.
us-gaap_LineOfCredit
Long-Term Line of Credit
us-gaap_ConvertibleDebt
Convertible Debt
us-gaap_DeferredFinanceCostsNet
Debt Issuance Costs, Net
us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net
Unamortized debt issuance costs attributable to term borrowings
Document Annual Report
The 2026 Notes Underwriter Option [Member]
Related to the 2026 notes underwriter option.
The 2027 Notes Underwriter Option [Member]
Related to the 2027 Notes underwriter option.
Entity Incorporation, State or Country Code
hrzn_LineOfCreditFacilityChangeInMaximumBorrowingCapacity
Line of Credit Facility, Change in Maximum Borrowing Capacity
The change in maximum borrowing capacity in line of credit facility.
Balance outstanding
Long-Term Debt, Gross
Other
Amount of other increase (decrease) of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.
Incentive Fee Cap and Deferral Mechanism, Contingent Future Liability
Amount of contingent future liability from Incentive Fee Cap and Deferral Mechanism.
Warrants and equity received and classified as Level 3
Amount of received warrants and equity received of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.
Document Transition Report
Document Financial Statement Error Correction [Flag]
hrzn_LineOfCreditFacilityMaximumBorrowingCapacityAccordionFeature
Line of Credit Facility, Maximum Borrowing Capacity, Accordion Feature
The accordion feature for the maximum borrowing capacity under line of credit facility.
Entity Interactive Data Current
hrzn_LineOfCreditFacilityAdvanceRate
Line of Credit Facility, Advance Rate
The advance rate under line of credit facility.
Estimated Time to Exit [Member]
Related to Estimated Time to Exit.
Last Equity Financing [Member]
Related to Last Equity Financing.
Investments, measurement input
Value of input used to measure investment assets.
Hypothetical Market Yield [Member]
Related to Hypothetical Market Yield.
Security Exchange Name
Multiple Probability Weighted Cash Flow Model [Member]
Related to Multiple Probability Weighted Cash Flow Model.
Probability Weighting [Member]
Related to Probability Weighting.
Title of 12(b) Security
Black-scholes Valuation Model [Member]
Related to Black-Scholes Valuation Model.
Interest Income [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Axis]
us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners
Subsidiary, Ownership Percentage, Noncontrolling Owner
Base management fee payable (Note 3)
Management Fee Payable
The 2028 Notes [Member]
Represents information pertaining to the 2028 notes.
Margin
Percentage added to reference rate used to compute variable rate on investment.
Technology Sector [Member]
Industry Sector [Domain]
Industry Sector [Axis]
Statement [Table]
us-gaap_MinorityInterestOwnershipPercentageByParent
Subsidiary, Ownership Percentage, Parent
Measurement Input, Hypothetical Market Yields [Member]
Related to hypothetical market yields used as measurement input.
hrzn_DebtInstrumentSharePrice
Debt Instrument, Share Price (in dollars per share)
The share price of a debt investment instrument.
Transfers in/(out) at fair value
Transfer amount changes to the investment in and advance to the affiliate.
Samba TV, Inc. [Member]
Represents information pertaining to Samba TV, Inc.
Income Statement [Abstract]
O 2025 M10 1 Dividends [Member]
Information regarding distributions.
O 2025 M10 3 Dividends [Member]
Information regarding distributions.
O 2025 M10 2 Dividends [Member]
Information regarding distributions.
O 2026 M3 Dividends [Member]
Information regarding distributions.
Discount accretion
Discount accretion to the investment in and advance to the affiliate.
O 2026 M5 Dividends [Member]
Information regarding distributions.
O 2026 M4 Dividends [Member]
Information regarding distributions.
O 2025 M7 3 Dividends [Member]
Information regarding distributions.
O 2025 M7 2 Dividends [Member]
Information regarding distributions.
Biotechnology Sector [Member]
Related to biotechnology sector.
Medical Device Sector [Member]
Related to medical device sector.
Communications Sector [Member]
Related to communications sector.
Consumer-related Sector [Member]
Related to consumer-related sector.
Life Science Segment [Member]
Related to life science segment.
Pelthos Therapeutics, Inc. [Member]
Represents information pertaining to Pelthos Therapeutics, Inc.
Sustainability Segment [Member]
Related to sustainability segment.
Healthcare Information and Services Segment [Member]
Related to Healthcare Information and Services segment.
Semiconductor Sector [Member]
Related to semiconductor sector.
us-gaap_OtherCommitment
Other Commitment
Software Sector [Member]
Related to software sector.
Other Sustainability Sector [Member]
Related to other sustainability sector.
Diagnostics Sector [Member]
Related to diagnostics sector.
Accounting Standards Update and Change in Accounting Principle [Table]
Data Storage Sector [Member]
Related to data storage sector.
Offsetting Liabilities [Table Text Block]
Internet and Media Sector [Member]
Related to internet and media sector.
Networking Sector [Member]
Related to networking sector.
Offsetting Liabilities [Table]
hrzn_IncentiveFeeToPreincentiveNetInvestmentIncome
Incentive Fee to Pre-incentive Net Investment Income
The incentive fee to pre-incentive net investment income.
hrzn_PreincentiveFeeNetInvestmentIncomeHurdleRate
Pre-Incentive Fee Net Investment Income, Hurdle Rate
The hurdle rate for pre-inventive fee net investment income.
hrzn_PreincentiveFeeNetInvestmentIncomeHurdleRateAnnualized
Pre-Incentive Fee Net Investment Income, Hurdle Rate, Annualized
The annualized pre-incentive fee net investment income hurdle rate.
hrzn_PreincentiveFeeNetInvestmentIncomeCatchupPercent
Pre-Incentive Fee Net Investment Income, Catch-up, Percent
The percent catch-up for pre-incentive fee net investment income.
hrzn_BaseManagementFeeAnnualPercent
Base Management Fee, Annual, Percent
The annual percentage base management fee.
hrzn_BaseManagementFeeAnnualPercentGrossAssetsExceeding250Million
Base Management Fee, Annual, Percent, Gross Assets Exceeding $250 Million
The annual percentage base management fee for gross assets exceeding $250 million.
Investment Management Agreement [Member]
Related to Investment Management Agreement.
hrzn_PreincentiveFeeNetInvestmentIncomeMaximumRateToTriggerCatchup
Pre-Incentive Fee Net Investment Income, Maximum Rate to Trigger Catch-up
The maximum rate to trigger catch-up for pre-incentive fee net investment income.
hrzn_PreincentiveFeeNetInvestmentIncomeMaximumRateToTriggerCatchupAnnualized
Pre-Incentive Fee Net Investment Income, Maximum Rate to Trigger Catch-up, Annualized
The annualized maximum rate to trigger catch-up for pre-incentive fee net investment income.
Administration Agreement [Member]
Related to administration agreement.
Net decrease in net assets resulting from operations per common share - diluted (1) (in dollars per share)
Per share or unit amount of increase (decrease) in net asset value, diluted.
The 2023 and 2021 Equity Distribution Agreements [Member]
Represents the 2023 and 2021 Equity Distribution Agreements.
December 31, 2027 Expiration [Member]
Represents information pertaining to the expiration of the total contingent future liability.
Commitments to Extend Credit [Member]
Ursa Space Systems Inc. [Member]
Related to Ursa Space Systems Inc.
Onkos Surgical, Inc. [Member]
Related to Onkos Surgical, Inc.
OneNetworks, Inc. dba Finexio [Member]
Related to OneNetworks, Inc. dba Finexio.
Crafty Holdings, Inc.[Member]
Related to Crafty Holdings, Inc.
O 2024 M10 3 Dividends [Member]
Information regarding distributions.
Offsetting Assets [Table]
us-gaap_StockholdersEquity
Balance
Balance
O 2024 M10 2 Dividends [Member]
Information regarding distributions.
O 2024 M10 1 Dividends [Member]
Information regarding distributions.
Mobia Medical Inc. [Member]
Represents information pertaining to Mobia Medical Inc.
HappyCo, Inc [Member]
Related to HappyCo, Inc.
us-gaap_InvestmentCompanyContractualAndVoluntaryFeesWaived
Investment Company, Contractual and Voluntary Fees Waived