Represents the number of shares transferred in an asset acquisition.

No definition available.

Name:	hrzn_AssetAcquisitionNumberOfSharesIssued
Namespace Prefix:	hrzn_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the number of shares issued for each share of the acquiree's common stock in relation to an asset acquisition.

+ References

No definition available.

+ Details

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Namespace Prefix:	hrzn_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the percentage owned after a merger or asset acquisition by the former stockholders of the acquiree.

+ References

No definition available.

+ Details

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Namespace Prefix:	hrzn_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the percentage owned after a merger or asset acquisition by the legacy stockholders.

+ References

No definition available.

+ Details

Name:	hrzn_AssetAcquisitionPercentageOwnedAfterMergerByLegacyStockholders
Namespace Prefix:	hrzn_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The cash inflow associated with the acquisition of business during the period (for example, cash that was held by the acquired business).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-12

+ Details

Name:	us-gaap_CashAcquiredFromAcquisition
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The cash outflow associated with the purchase of all investments (debt, security, other) during the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-13

+ Details

Name:	us-gaap_PaymentsToAcquireInvestments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of cash outflow for short-term and long-term debt. Excludes payment of lease obligation.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 15
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-15

+ Details

Name:	us-gaap_RepaymentsOfDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=hrzn_KeyFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AssetAcquisitionAxis=hrzn_MrccMergerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_DebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentIssuerNameAxis=hrzn_BastilleBuyerIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentIssuerNameAxis=hrzn_VoltBidcoIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Note 13 - Subsequent Events (Details Textual) - Subsequent Event [Member] - USD ($) $ in Millions	Apr. 30, 2026	Apr. 14, 2026	Apr. 01, 2026
Key Facility [Member]
Repayments of Debt		$ 45.0
MRCC Merger [Member]
Cash Acquired from Acquisition		$ 141.1
Asset Acquisition, Number of Shares Issued (in shares)		20,370,645
Business Combination, Number of Shares Issued For Each Share of Acquiree's Common Stock (in shares)		0.9402
Business Combination, Percentage Owned After Merger by Former Stockholders of Acquiree		29.86%
Business Combination, Percentage Owned After Merger by Legacy Stockholders		70.14%
Stellar Cyber, Inc. [Member] \| Debt Securities [Member]
Payments to Acquire Investments			$ 15.0
Bastille Buyer, Inc. [Member] \| Debt Securities [Member]
Payments to Acquire Investments	$ 3.0
Volt Bidco, Inc. [Member] \| Debt Securities [Member]
Payments to Acquire Investments	$ 4.0