XML 55 R42.htm IDEA: XBRL DOCUMENT
v3.25.2

Note 5 - Transactions With Affiliated Companies - Investments in Controlled Affiliated Companies (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2025 | Mar. 31, 2025 | Jun. 30, 2024 | Mar. 31, 2024 | Jun. 30, 2025 | Jun. 30, 2024
Investments, fair value |  | $ 697,891 |  |  | $ 697,891 |
Net unrealized appreciation (depreciation) on investments | $ (22,156) |  | $ (24,511) |  | (54,313) | $ (28,471)
Net realized gain (loss) | (9,294) |  | 2,464 |  | (9,293) | 2,472
Investments, fair value | 622,653 |  |  |  | 622,653 |
Interest Income, Operating, Paid in Kind |  |  |  |  | 528 | 1,737
Investment, Affiliated Issuer, Noncontrolled [Member] |  |  |  |  |  |
Investments, fair value | 8,307 | 8,307 | 12,577 | $ 1,132 | 8,307 | 1,132
Purchases | 0 |  | 92 |  | 2 | 107
Reductions | 0 |  | (40) |  | 0 | (40)
Transfers in/(out) at fair value | 0 |  | 0 |  | 0 | 0
Discount accretion | 0 |  | 0 |  | 0 | 0
Net unrealized appreciation (depreciation) on investments | (1,600) |  | 3,178 |  | (1,602) | 14,611
Net realized gain (loss) | 0 |  | 40 |  | 0 | 37
Investments, fair value | 6,707 | 8,307 | 15,847 | 12,577 | 6,707 | 15,847
Interest income | 0 |  | 0 |  | 0 | 0
Investment, Affiliated Issuer, Noncontrolled [Member] | Aulea Medical, Inc. [Member] |  |  |  |  |  |
Investments, fair value | 0 | 0 | 0 | 0 | 0 | 0
Purchases | 0 |  | 0 |  | 0 | 3
Reductions | 0 |  | (40) |  | 0 | (40)
Transfers in/(out) at fair value | 0 |  | 0 |  | 0 | 0
Discount accretion | 0 |  | 0 |  | 0 | 0
Net unrealized appreciation (depreciation) on investments | 0 |  | 0 |  | 0 | 0
Net realized gain (loss) | 0 |  | 40 |  | 0 | 37
Investments, fair value | 0 | 0 | 0 | 0 | 0 | 0
Interest income | 0 |  | 0 |  | 0 | 0
Investment, Affiliated Issuer, Noncontrolled [Member] | Evelo Biosciences, Inc. [Member] |  |  |  |  |  |
Investments, fair value | 8,307 | 8,307 | 12,577 | 1,132 | 8,307 | 1,132
Purchases | 0 |  | 92 |  | 2 | 104
Reductions | 0 |  | 0 |  | 0 | 0
Transfers in/(out) at fair value | 0 |  | 0 |  | 0 | 0
Discount accretion | 0 |  | 0 |  | 0 | 0
Net unrealized appreciation (depreciation) on investments | (1,600) |  | 3,178 |  | (1,602) | 14,611
Net realized gain (loss) | 0 |  | 0 |  | 0 | 0
Investments, fair value | 6,707 | 8,307 | 15,847 | 12,577 | 6,707 | 15,847
Interest income | 0 |  | 0 |  | 0 | 0
Investment, Affiliated Issuer, Controlled [Member] |  |  |  |  |  |
Investments, fair value | 14,869 | 31,819 | 13,644 | 14,223 | 31,819 | 14,223
Purchases | 1,255 |  | 1,500 |  | 4,205 | 2,477
Reductions | 0 |  | 0 |  | 0 | (547)
Transfers in/(out) at fair value | 0 |  | 463 |  | 0 | 463
Discount accretion | 0 |  | 3 |  | 9 | 7
Net unrealized appreciation (depreciation) on investments | (5,669) |  | (4,402) |  | (25,786) | (5,581)
Net realized gain (loss) | 0 |  | 0 |  | 0 | 0
Investments, fair value | 10,455 | 14,869 | 11,386 | 13,644 | 10,455 | 11,386
Interest income | 20 |  | 188 |  |  | 365
Interest Income, Operating, Paid in Kind | 0 |  | 178 |  | 208 | 344
Interest Income, Net | (41) |  |  |  | (41) |
Investment, Affiliated Issuer, Controlled [Member] | Better Place Forests Co. [Member] |  |  |  |  |  |
Investments, fair value | 879 | 0 | 7,799 | 7,993 | 0 | 7,993
Purchases | 1,107 |  | 1,500 |  | 2,048 | 2,250
Reductions | 0 |  | 0 |  | 0 | 0
Transfers in/(out) at fair value | 0 |  | 0 |  | 0 | 0
Discount accretion | 0 |  | 3 |  | 0 | 7
Net unrealized appreciation (depreciation) on investments | (1,107) |  | (3,930) |  | (1,169) | (5,044)
Net realized gain (loss) | 0 |  | 0 |  | 0 | 0
Investments, fair value | 879 | 879 | 5,550 | 7,799 | 879 | 5,550
Interest income | 0 |  | 188 |  |  | 365
Interest Income, Operating, Paid in Kind | 0 |  | 178 |  | 0 | 344
Interest Income, Net | 0 |  |  |  | 0 |
Investment, Affiliated Issuer, Controlled [Member] | HIMV LLC [Member] |  |  |  |  |  |
Investments, fair value | 5,290 | 6,230 | 5,845 | 6,230 | 6,230 | 6,230
Purchases | 0 |  | 0 |  | 0 | 227
Reductions | 0 |  | 0 |  | 0 | (547)
Transfers in/(out) at fair value | 0 |  | 463 |  | 0 | 463
Discount accretion | 0 |  | 0 |  | 0 | 0
Net unrealized appreciation (depreciation) on investments | (4,425) |  | (472) |  | (5,365) | (537)
Net realized gain (loss) | 0 |  | 0 |  | 0 | 0
Investments, fair value | 865 | 5,290 | 5,836 | $ 5,845 | 865 | 5,836
Interest income | 0 |  | 0 |  |  | 0
Interest Income, Operating, Paid in Kind | 0 |  | $ 0 |  | 0 | $ 0
Interest Income, Net | 0 |  |  |  | 0 |
Investment, Affiliated Issuer, Controlled [Member] | Nexii Building Solutions, Inc [Member] |  |  |  |  |  |
Investments, fair value | 8,700 | 8,547 |  |  | 8,547 |
Purchases | 11 |  |  |  | 11 |
Reductions | 0 |  |  |  | 0 |
Transfers in/(out) at fair value | 0 |  |  |  | 0 |
Discount accretion | 0 |  |  |  | 0 |
Net unrealized appreciation (depreciation) on investments | 0 |  |  |  | 153 |
Net realized gain (loss) | 0 |  |  |  | 0 |
Investments, fair value | 8,711 | 8,700 |  |  | 8,711 |
Interest income | 20 |  |  |  |  |
Interest Income, Operating, Paid in Kind | 0 |  |  |  | 0 |
Interest Income, Net | 40 |  |  |  | 40 |
Investment, Affiliated Issuer, Controlled [Member] | Swift Health Systems Inc. [Member] |  |  |  |  |  |
Investments, fair value | 0 | 17,042 |  |  | 17,042 |
Purchases | 137 |  |  |  | 2,146 |
Reductions | 0 |  |  |  | 0 |
Transfers in/(out) at fair value | 0 |  |  |  | 0 |
Discount accretion | 0 |  |  |  | 9 |
Net unrealized appreciation (depreciation) on investments | (137) |  |  |  | (19,405) |
Net realized gain (loss) | 0 |  |  |  | 0 |
Investments, fair value | 0 | $ 0 |  |  | 0 |
Interest income | 0 |  |  |  |  |
Interest Income, Operating, Paid in Kind | 0 |  |  |  | 208 |
Interest Income, Net | $ (81) |  |  |  | $ (81) |

X
- Definition The amount of interest income, net. + References No definition available. + Details
Name: | hrzn_InterestIncomeNet
Namespace Prefix: | hrzn_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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/1943274/2147477271/946-320-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/1943274/2147477271/946-320-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/1943274/2147477271/946-320-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/1943274/2147479134/946-220-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://www.xbrl.org/2003/role/exampleRef -Topic 280 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 48 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482785/280-10-55-48 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -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 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 270 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (i) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482964/270-10-50-1 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 280 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 32 -Subparagraph (ee) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482810/280-10-50-32 + 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 S99 -Paragraph 1 -Subparagraph (SX 210.6-04(11)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479170/946-210-S99-1 Reference 2: 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/1943274/2147478795/946-210-50-6 Reference 3: 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/1943274/2147477439/946-210-55-1 Reference 4: 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/1943274/2147478795/946-210-50-6 Reference 5: 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/1943274/2147478795/946-210-50-6 Reference 6: 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/1943274/2147478795/946-210-50-1 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478795/946-210-50-1 Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478795/946-210-50-1 Reference 9: 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/1943274/2147478795/946-210-50-1 Reference 10: 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/1943274/2147478795/946-210-50-2 Reference 11: 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/1943274/2147479168/946-830-55-12 Reference 12: 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/1943274/2147478795/946-210-50-6 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/1943274/2147479170/946-210-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/1943274/2147479170/946-210-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/1943274/2147479170/946-210-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/1943274/2147477271/946-320-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/1943274/2147477271/946-320-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/1943274/2147477271/946-320-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/1943274/2147477271/946-320-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/1943274/2147477271/946-320-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/1943274/2147477271/946-320-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/1943274/2147477271/946-320-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/1943274/2147477271/946-320-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/1943274/2147477271/946-320-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/1943274/2147477271/946-320-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/1943274/2147477271/946-320-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/1943274/2147477271/946-320-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/1943274/2147477271/946-320-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/1943274/2147477271/946-320-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/1943274/2147477271/946-320-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/1943274/2147477271/946-320-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/1943274/2147477250/944-220-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_InvestmentIssuerAffiliationAxis=us-gaap_InvestmentAffiliatedIssuerNoncontrolledMember
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_EveloBiosciencesIncMember
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_InvestmentIssuerNameAxis=hrzn_BetterPlaceForestsCoMember
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: |

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

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