The change in maximum borrowing capacity in line of credit facility.

No definition available.

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Namespace Prefix:	hrzn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of cash inflow from debt securities.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
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Period Type:	duration

- Definition

Amount authorized for purchase of share under share repurchase plan. Includes, but is not limited to, repurchase of stock and unit of ownership.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 505
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481520/505-30-50-4

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash inflow associated with the sale, maturity and collection of all investments such as debt, security and so forth during the period.

+ References

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

+ Details

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Period Type:	duration

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Namespace Prefix:
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Balance Type:
Period Type:

- Details

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Balance Type:
Period Type:

- Details

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Balance Type:
Period Type:

- Details

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Balance Type:
Period Type:

- Details

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Balance Type:
Period Type:

- Details

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Balance Type:
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- Details

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- Details

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- Details

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Note 14 - Subsequent Events (Details Textual) - USD ($) $ in Millions	Aug. 03, 2026	Jul. 31, 2026	Jul. 17, 2026	Jul. 15, 2026	Jul. 08, 2026	Jul. 01, 2026	May 23, 2025	May 01, 2026
Share Repurchase Program, Authorized, Amount								$ 10.0
Nuveen Facility [Member]
Line of Credit Facility, Change in Maximum Borrowing Capacity							$ 100.0
Subsequent Event [Member]
Share Repurchase Program, Authorized, Amount	$ 20.0
Subsequent Event [Member] \| Nuveen Facility [Member]
Line of Credit Facility, Change in Maximum Borrowing Capacity			$ 50.0
Debt Securities [Member] \| Glass Routes, LLC [Member] \| Subsequent Event [Member]
Payments to Acquire Investments	0.7					$ 0.6
Debt Securities [Member] \| Onkos Surgical, Inc. [Member] \| Subsequent Event [Member]
Payments to Acquire Investments					$ 5.0
Debt Securities [Member] \| Ossio Inc [Member] \| Subsequent Event [Member]
Payments to Acquire Investments				$ 2.5
Debt Securities [Member] \| StarCompliance Midco, LLC [Member] \| Subsequent Event [Member]
Payments to Acquire Investments				$ 23.3
Debt Securities [Member] \| Avive Solutions Inc [Member] \| Subsequent Event [Member]
Payments to Acquire Investments			$ 6.8
Debt Securities [Member] \| Volt Bidco, Inc. [Member] \| Subsequent Event [Member]
Payments to Acquire Investments		$ 0.1
Debt Securities [Member] \| Mirantis, Inc [Member] \| Subsequent Event [Member]
Proceeds from Sale, Maturity and Collection of Investments	15.0
Debt Securities [Member] \| Havenly, Inc. [Member] \| Subsequent Event [Member]
Proceeds from Sale, Maturity and Collection of Investments	11.8
Proceeds from Debt Securities, End-of-term, Amount	$ 1.2