XML 47 R37.htm IDEA: XBRL DOCUMENT
v3.23.3

Note 5 - Transactions With Affiliated Companies - Investments in Controlled Affiliated Companies (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2023 | Sep. 30, 2022 | Sep. 30, 2023 | Sep. 30, 2022
Investments, fair value |  |  |  | $ 720,026 |
Net unrealized appreciation (depreciation) on investments |  | $ (17,518) | $ 3,442 | (24,448) | $ 1,169
Net realized gain (loss) on investments |  | (11,816) | (8,585) | (28,513) | (9,484)
Investments, fair value |  | 729,053 |  | 729,053 |
Interest Income, Operating, Paid in Kind |  | 3,900 | 0 | 6,088 | 0
Investments, fair value |  | (729,053) |  | (729,053) |
Evelo Biosciences, Inc. [Member] |  |  |  |  |
Investments, fair value |  | 8,500 |  | 8,500 |
Investments, fair value |  | (8,500) |  | (8,500) |
Investment, Affiliated Issuer, Noncontrolled [Member] |  |  |  |  |
Investments, fair value |  | 906 | 0 | 0 | 0
Purchases |  | 0 | 0 | 0 | 0
Reductions |  | 0 | (30) | 0 | (30)
Transfers in/(out) at fair value |  | 38,599 | 0 | 38,599 | 0
Discount accretion |  | 35 | 0 | 35 | 0
Net unrealized appreciation (depreciation) on investments |  | (19,055) | 0 | (18,149) | 0
Net realized gain (loss) on investments |  | 0 | 30 | 0 | 30
Investments, fair value |  | 20,485 | 0 | 20,485 | 0
Interest income |  | 1,246 | 0 | 1,246 | 0
Transfers in/(out) at fair value |  | 38,599 | 0 | 38,599 | 0
Investments, fair value |  | (20,485) | 0 | (20,485) | 0
Investment, Affiliated Issuer, Noncontrolled [Member] | MVI (ABC) LLC fka StereoVision, Inc [Member] |  |  |  |  |
Investments, fair value |  |  | 0 |  | 0
Purchases |  |  | 0 |  | 0
Reductions |  |  | (30) |  | (30)
Transfers in/(out) at fair value |  |  | 0 |  | 0
Discount accretion |  |  | 0 |  | 0
Net unrealized appreciation (depreciation) on investments |  |  | 0 |  | 0
Net realized gain (loss) on investments |  |  | 30 |  | 30
Investments, fair value |  |  | 0 |  | 0
Interest income |  |  | 0 |  | 0
Transfers in/(out) at fair value |  |  | 0 |  | 0
Investments, fair value |  |  | 0 |  | 0
Investment, Affiliated Issuer, Noncontrolled [Member] | Aulea Medical, Inc. [Member] |  |  |  |  |
Investments, fair value |  | 0 |  | 0 |
Purchases |  | 0 |  | 0 |
Reductions |  | 0 |  | 0 |
Transfers in/(out) at fair value |  | 0 |  | 0 |
Discount accretion |  | 0 |  | 0 |
Net unrealized appreciation (depreciation) on investments |  | 0 |  | 0 |
Net realized gain (loss) on investments |  | 0 |  | 0 |
Investments, fair value |  | 0 |  | 0 |
Interest income |  | 0 |  | 0 |
Transfers in/(out) at fair value |  | 0 |  | 0 |
Investments, fair value |  | 0 |  | 0 |
Investment, Affiliated Issuer, Noncontrolled [Member] | Cadrenal Therapeutics, Inc. [Member] |  |  |  |  |
Investments, fair value | [1] | 906 |  | 0 |
Purchases | [1] | 0 |  | 0 |
Reductions | [1] | 0 |  | 0 |
Transfers in/(out) at fair value | [1] | (906) |  | (906) |
Discount accretion | [1] | 0 |  | 0 |
Net unrealized appreciation (depreciation) on investments | [1] | 0 |  | 906 |
Net realized gain (loss) on investments | [1] | 0 |  | 0 |
Investments, fair value | [1] | 0 |  | 0 |
Interest income | [1] | 0 |  | 0 |
Transfers in/(out) at fair value | [1] | (906) |  | (906) |
Investments, fair value | [1] | 0 |  | 0 |
Investment, Affiliated Issuer, Noncontrolled [Member] | Evelo Biosciences, Inc. [Member] | Investment One [Member] |  |  |  |  |
Investments, fair value |  | 0 |  | 0 |
Purchases |  | 0 |  | 0 |
Reductions |  | 0 |  | 0 |
Transfers in/(out) at fair value |  | 7,665 |  | 7,665 |
Discount accretion |  | 8 |  | 8 |
Net unrealized appreciation (depreciation) on investments |  | (5,007) |  | (5,007) |
Net realized gain (loss) on investments |  | 0 |  | 0 |
Investments, fair value |  | 2,666 |  | 2,666 |
Interest income |  | 277 |  | 277 |
Transfers in/(out) at fair value |  | 7,665 |  | 7,665 |
Investments, fair value |  | (2,666) |  | (2,666) |
Investment, Affiliated Issuer, Noncontrolled [Member] | Evelo Biosciences, Inc. [Member] | Investment Two [Member] |  |  |  |  |
Investments, fair value |  | 0 |  | 0 |
Purchases |  | 0 |  | 0 |
Reductions |  | 0 |  | 0 |
Transfers in/(out) at fair value |  | 11,496 |  | 11,496 |
Discount accretion |  | 11 |  | 11 |
Net unrealized appreciation (depreciation) on investments |  | (7,510) |  | (7,510) |
Net realized gain (loss) on investments |  | 0 |  | 0 |
Investments, fair value |  | 3,997 |  | 3,997 |
Interest income |  | 415 |  | 415 |
Transfers in/(out) at fair value |  | 11,496 |  | 11,496 |
Investments, fair value |  | (3,997) |  | (3,997) |
Investment, Affiliated Issuer, Noncontrolled [Member] | Evelo Biosciences, Inc. [Member] | Investment Three [Member] |  |  |  |  |
Investments, fair value |  | 0 |  | 0 |
Purchases |  | 0 |  | 0 |
Reductions |  | 0 |  | 0 |
Transfers in/(out) at fair value |  | 4,612 |  | 4,612 |
Discount accretion |  | 5 |  | 5 |
Net unrealized appreciation (depreciation) on investments |  | (3,013) |  | (3,013) |
Net realized gain (loss) on investments |  | 0 |  | 0 |
Investments, fair value |  | 1,604 |  | 1,604 |
Interest income |  | 166 |  | 166 |
Transfers in/(out) at fair value |  | 4,612 |  | 4,612 |
Investments, fair value |  | (1,604) |  | (1,604) |
Investment, Affiliated Issuer, Noncontrolled [Member] | Evelo Biosciences, Inc. [Member] | Investment Four [Member] |  |  |  |  |
Investments, fair value |  | 0 |  | 0 |
Purchases |  | 0 |  | 0 |
Reductions |  | 0 |  | 0 |
Transfers in/(out) at fair value |  | 4,598 |  | 4,598 |
Discount accretion |  | 3 |  | 3 |
Net unrealized appreciation (depreciation) on investments |  | (3,004) |  | (3,004) |
Net realized gain (loss) on investments |  | 0 |  | 0 |
Investments, fair value |  | 1,597 |  | 1,597 |
Interest income |  | 163 |  | 163 |
Transfers in/(out) at fair value |  | 4,598 |  | 4,598 |
Investments, fair value |  | (1,597) |  | (1,597) |
Investment, Affiliated Issuer, Noncontrolled [Member] | Evelo Biosciences, Inc. [Member] | Investment Five [Member] |  |  |  |  |
Investments, fair value |  | 0 |  | 0 |
Purchases |  | 0 |  | 0 |
Reductions |  | 0 |  | 0 |
Transfers in/(out) at fair value |  | 3,067 |  | 3,067 |
Discount accretion |  | 4 |  | 4 |
Net unrealized appreciation (depreciation) on investments |  | (2,003) |  | (2,003) |
Net realized gain (loss) on investments |  | 0 |  | 0 |
Investments, fair value |  | 1,068 |  | 1,068 |
Interest income |  | 114 |  | 114 |
Transfers in/(out) at fair value |  | 3,067 |  | 3,067 |
Investments, fair value |  | (1,068) |  | (1,068) |
Investment, Affiliated Issuer, Noncontrolled [Member] | Evelo Biosciences, Inc. [Member] | Investment Six [Member] |  |  |  |  |
Investments, fair value |  | 0 |  | 0 |
Purchases |  | 0 |  | 0 |
Reductions |  | 0 |  | 0 |
Transfers in/(out) at fair value |  | 3,067 |  | 3,067 |
Discount accretion |  | 4 |  | 4 |
Net unrealized appreciation (depreciation) on investments |  | (2,003) |  | (2,003) |
Net realized gain (loss) on investments |  | 0 |  | 0 |
Investments, fair value |  | 1,068 |  | 1,068 |
Interest income |  | 111 |  | 111 |
Transfers in/(out) at fair value |  | 3,067 |  | 3,067 |
Investments, fair value |  | (1,068) |  | (1,068) |
Investment, Affiliated Issuer, Noncontrolled [Member] | Evelo Biosciences, Inc. [Member] | Investment Seven [Member] |  |  |  |  |
Investments, fair value |  | 0 |  | 0 |
Purchases |  | 0 |  | 0 |
Reductions |  | 0 |  | 0 |
Transfers in/(out) at fair value |  | 5,000 |  | 5,000 |
Discount accretion |  | 0 |  | 0 |
Net unrealized appreciation (depreciation) on investments |  | 3,485 |  | 3,485 |
Net realized gain (loss) on investments |  | 0 |  | 0 |
Investments, fair value |  | 8,485 |  | 8,485 |
Interest income |  | 0 |  | 0 |
Transfers in/(out) at fair value |  | 5,000 |  | 5,000 |
Investments, fair value |  | (8,485) |  | (8,485) |
Investment, Affiliated Issuer, Controlled [Member] |  |  |  |  |
Investments, fair value |  | 0 | 0 | 0 | 0
Purchases |  | 809 | 0 | 809 | 0
Reductions |  | 0 | (50) | 0 | (300)
Transfers in/(out) at fair value |  | 10,818 | 0 | 10,818 | 0
Discount accretion |  | 3 | 0 | 3 | 0
Net unrealized appreciation (depreciation) on investments |  | 1,357 | 0 | 1,357 | 1,450
Net realized gain (loss) on investments |  | 0 | 50 | 0 | (1,150)
Investments, fair value |  | 13,145 | 0 | 13,145 | 0
Interest income |  | 8 | 0 | 8 | 0
Interest Income, Operating, Paid in Kind |  | 158 | 0 | 158 | 0
Transfers in/(out) at fair value |  | 10,818 | 0 | 10,818 | 0
Investments, fair value |  | (13,145) | 0 | (13,145) | 0
Investment, Affiliated Issuer, Controlled [Member] | Investment [Member] |  |  |  |  |
Interest income |  | 166 |  | 166 |
Investment, Affiliated Issuer, Controlled [Member] | Better Place Forests Co. [Member] | Investment One [Member] |  |  |  |  |
Investments, fair value |  | 0 |  | 0 |
Purchases |  | 59 |  | 59 |
Reductions |  | 0 |  | 0 |
Transfers in/(out) at fair value |  | 1,759 |  | 1,759 |
Discount accretion |  | 2 |  | 2 |
Net unrealized appreciation (depreciation) on investments |  | 1,080 |  | 1,080 |
Net realized gain (loss) on investments |  | 0 |  | 0 |
Investments, fair value |  | 3,005 |  | 3,005 |
Interest income |  | 111 |  | 111 |
Interest Income, Operating, Paid in Kind |  | 105 |  | 105 |
Transfers in/(out) at fair value |  | 1,759 |  | 1,759 |
Investments, fair value |  | (3,005) |  | (3,005) |
Investment, Affiliated Issuer, Controlled [Member] | Better Place Forests Co. [Member] | Investment Two [Member] |  |  |  |  |
Investments, fair value |  | 0 |  | 0 |
Purchases |  | 0 |  | 0 |
Reductions |  | 0 |  | 0 |
Transfers in/(out) at fair value |  | 844 |  | 844 |
Discount accretion |  | 1 |  | 1 |
Net unrealized appreciation (depreciation) on investments |  | 536 |  | 536 |
Net realized gain (loss) on investments |  | 0 |  | 0 |
Investments, fair value |  | 1,434 |  | 1,434 |
Interest income |  | 55 |  | 55 |
Interest Income, Operating, Paid in Kind |  | 53 |  | 53 |
Transfers in/(out) at fair value |  | 844 |  | 844 |
Investments, fair value |  | (1,434) |  | (1,434) |
Investment, Affiliated Issuer, Controlled [Member] | Better Place Forests Co. [Member] | Investment Three [Member] |  |  |  |  |
Investments, fair value |  | 0 |  | 0 |
Purchases |  | 0 |  | 0 |
Reductions |  | 0 |  | 0 |
Transfers in/(out) at fair value |  | 2,061 |  | 2,061 |
Discount accretion |  | 0 |  | 0 |
Net unrealized appreciation (depreciation) on investments |  | 0 |  | 0 |
Net realized gain (loss) on investments |  | 0 |  | 0 |
Investments, fair value |  | 2,061 |  | 2,061 |
Interest income |  | 0 |  | 0 |
Interest Income, Operating, Paid in Kind |  | 0 |  | 0 |
Transfers in/(out) at fair value |  | 2,061 |  | 2,061 |
Investments, fair value |  | (2,061) |  | (2,061) |
Investment, Affiliated Issuer, Controlled [Member] | Better Place Forests Co. [Member] | Investment Four [Member] |  |  |  |  |
Investments, fair value |  | 0 |  | 0 |
Purchases |  | 750 |  | 750 |
Reductions |  | 0 |  | 0 |
Transfers in/(out) at fair value |  | 0 |  | 0 |
Discount accretion |  | 0 |  | 0 |
Net unrealized appreciation (depreciation) on investments |  | (259) |  | (259) |
Net realized gain (loss) on investments |  | 0 |  | 0 |
Investments, fair value |  | 491 |  | 491 |
Interest income |  | 0 |  | 0 |
Interest Income, Operating, Paid in Kind |  | 0 |  | 0 |
Transfers in/(out) at fair value |  | 0 |  | 0 |
Investments, fair value |  | (491) |  | (491) |
Investment, Affiliated Issuer, Controlled [Member] | HESP LLC [Member] |  |  |  |  |
Investments, fair value |  |  | 0 |  | 0
Purchases |  |  | 0 |  | 0
Reductions |  |  | (50) |  | (300)
Transfers in/(out) at fair value |  |  | 0 |  | 0
Discount accretion |  |  | 0 |  | 0
Net unrealized appreciation (depreciation) on investments |  |  | 0 |  | 1,450
Net realized gain (loss) on investments |  |  | 50 |  | (1,150)
Investments, fair value |  |  | 0 |  | 0
Interest income |  |  | 0 |  | 0
Transfers in/(out) at fair value |  |  | 0 |  | 0
Investments, fair value |  |  | $ 0 |  | $ 0
Investment, Affiliated Issuer, Controlled [Member] | HIMV LLC [Member] |  |  |  |  |
Investments, fair value |  | 0 |  | 0 |
Purchases |  | 0 |  | 0 |
Reductions |  | 0 |  | 0 |
Transfers in/(out) at fair value |  | 6,154 |  | 6,154 |
Discount accretion |  | 0 |  | 0 |
Net unrealized appreciation (depreciation) on investments |  | 0 |  | 0 |
Net realized gain (loss) on investments |  | 0 |  | 0 |
Investments, fair value |  | 6,154 |  | 6,154 |
Interest income |  | 0 |  | 0 |
Interest Income, Operating, Paid in Kind |  | 0 |  | 0 |
Transfers in/(out) at fair value |  | 6,154 |  | 6,154 |
Investments, fair value |  | $ (6,154) |  | $ (6,154) |
[1] | As of September 30, 2023, the Company no longer owns 5% or more of the portfolio company.

X
- Definition Discount accretion to the investment in and advance to the affiliate. + References No definition available. + Details
Name: | hrzn_InvestmentsInAndAdvancesToAffiliatesAtFairValueDiscountAccretion
Namespace Prefix: | hrzn_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Transfer amount changes to the investment in and advance to the affiliate. + References No definition available. + Details
Name: | hrzn_InvestmentsInAndAdvancesToAffiliatesAtFairValueTransfers
Namespace Prefix: | hrzn_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of interest income from investment paid in kind, classified as operating. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column E)(1)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-6 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column E)(Footnote 6)(a)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-6 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column E)(Footnote 6)(c)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-6 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.6-07(1)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147483575/946-220-S99-1 + Details
Name: | us-gaap_InterestIncomeOperatingPaidInKind
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount before accretion (amortization) of purchase discount (premium) of interest income on nonoperating securities. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 280 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 22 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482810/280-10-50-22 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.7(b)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147483621/220-10-S99-2 + Details
Name: | us-gaap_InvestmentIncomeInterest
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Fair value of investment in security owned. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480524/946-210-50-6 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 55 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480493/946-210-55-1 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (a)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480524/946-210-50-6 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (a)(2) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480524/946-210-50-6 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (a)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480524/946-210-50-1 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480524/946-210-50-1 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b)(2) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480524/946-210-50-1 Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c)(2) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480524/946-210-50-1 Reference 9: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480524/946-210-50-2 Reference 10: http://www.xbrl.org/2003/role/exampleRef -Topic 946 -SubTopic 830 -Name Accounting Standards Codification -Section 55 -Paragraph 12 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480167/946-830-55-12 Reference 11: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (a)(3) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480524/946-210-50-6 Reference 12: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.6-04(11)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479617/946-210-S99-1 Reference 13: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.6-03(d)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479886/946-10-S99-3 Reference 14: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.6-04(1)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479617/946-210-S99-1 Reference 15: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.6-04(2)(a)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479617/946-210-S99-1 Reference 16: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.6-04(2)(b)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479617/946-210-S99-1 Reference 17: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-12(Column C)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-1 Reference 18: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-12(Column A)(Footnote 1)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-1 Reference 19: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-12(Column C)(Footnote 5)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-1 Reference 20: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-12(Column C)(Footnote 6)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-1 Reference 21: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-12B(Column C)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-3 Reference 22: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-12B(Column C)(Footnote 2)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-3 Reference 23: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-12B(Column A)(Footnote 6)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-3 Reference 24: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-12B(Column A)(Footnote 7)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-3 Reference 25: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-12B(Column C)(Footnote 9)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-3 Reference 26: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column F)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-6 Reference 27: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column A)(Footnote 1)(b)(2)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-6 Reference 28: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column A)(Footnote 1)(b)(5)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-6 Reference 29: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column F)(Footnote 4)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-6 Reference 30: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column F)(Footnote 7)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-6 + Details
Name: | us-gaap_InvestmentOwnedAtFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Gross additions to the investment in and advance to the affiliate. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column A)(Footnote 1)(b)(3)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-6 + Details
Name: | us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossAdditions
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Gross reductions to the investment in and advance to the affiliate. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column A)(Footnote 1)(b)(4)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480032/946-320-S99-6 + Details
Name: | us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossReductions
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of realized gain (loss) on investment. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(3)(a)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147483586/944-220-S99-1 + Details
Name: | us-gaap_RealizedInvestmentGainsLosses
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of unrealized gain (loss) on investment. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 45 -Paragraph 28 -Subparagraph (b) -SubTopic 10 -Topic 230 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482740/230-10-45-28 + Details
Name: | us-gaap_UnrealizedGainLossOnInvestments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | us-gaap_InvestmentIssuerNameAxis=hrzn_EveloBiosciencesIncMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIssuerAffiliationAxis=us-gaap_InvestmentAffiliatedIssuerNoncontrolledMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIssuerNameAxis=hrzn_MVIBCLLCfkaStereoVisionIncMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIssuerNameAxis=hrzn_AuleaMedicalIncMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIssuerNameAxis=hrzn_CadrenalTherapeuticsIncMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=hrzn_InvestmentOneMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=hrzn_InvestmentTwoMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=hrzn_InvestmentThreeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=hrzn_InvestmentFourMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=hrzn_InvestmentFiveMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=hrzn_InvestmentSixMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=hrzn_InvestmentSevenMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIssuerAffiliationAxis=us-gaap_InvestmentAffiliatedIssuerControlledMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=hrzn_InvestmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIssuerNameAxis=hrzn_BetterPlaceForestsCoMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIssuerNameAxis=hrzn_HESPLLCMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIssuerNameAxis=hrzn_HIMVLLCMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |