XML 51 R40.htm IDEA: XBRL DOCUMENT
v3.24.3

Note 5 - Transactions With Affiliated Companies - Investments in Affiliated Companies (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2024 | Sep. 30, 2023 | Sep. 30, 2024 | Sep. 30, 2023
Investments, fair value |  |  |  | $ 709,085 |
Net unrealized appreciation (depreciation) on investments |  | $ 29,335 | $ (17,518) | 864 | $ (24,448)
Net realized gain (loss) on investments |  | (33,894) | (11,816) | (31,422) | (28,513)
Investments, fair value |  | 684,000 |  | 684,000 |
Interest Income, Operating, Paid in Kind |  |  |  | 2,114 | 6,088
Investment, Affiliated Issuer, Noncontrolled [Member] |  |  |  |  |
Investments, fair value |  | 15,847 | 906 | 1,132 | 0
Purchases |  | 127 | 0 | 234 | 0
Reductions |  | (1,430) | 0 | (1,470) | 0
Transfers in/(out) at fair value |  | 0 | 38,599 | 0 | 38,599
Discount accretion |  | 0 | 35 | 0 | 35
Net unrealized appreciation (depreciation) on investments |  | (6,237) | (19,055) | 8,374 | (18,149)
Net realized gain (loss) on investments |  | 0 | 0 | 37 | 0
Investments, fair value |  | 8,307 | 20,485 | 8,307 | 20,485
Interest income |  | 0 | 1,246 | 0 | 1,246
Investment, Affiliated Issuer, Noncontrolled [Member] | Aulea Medical, Inc. [Member] |  |  |  |  |
Investments, fair value |  | 0 | 0 | 0 | 0
Purchases |  | 0 | 0 | 3 | 0
Reductions |  | 0 | 0 | (40) | 0
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) on investments |  | 0 | 0 | 37 | 0
Investments, fair value |  | 0 | 0 | 0 | 0
Interest income |  |  | 0 | 0 | 0
Investment, Affiliated Issuer, Noncontrolled [Member] | Evelo Biosciences, Inc. [Member] | Investment One [Member] |  |  |  |  |
Investments, fair value |  | 3,503 | 0 | 222 | 0
Purchases |  | 0 | 0 | 0 | 0
Reductions |  | (318) | 0 | (318) | 0
Transfers in/(out) at fair value |  | 0 | 7,665 | 0 | 7,665
Discount accretion |  | 0 | 8 | 0 | 8
Net unrealized appreciation (depreciation) on investments |  | (1,360) | (5,007) | 1,921 | (5,007)
Net realized gain (loss) on investments |  | 0 | 0 | 0 | 0
Investments, fair value |  | 1,825 | 2,666 | 1,825 | 2,666
Interest income |  |  | 277 | 0 | 277
Investment, Affiliated Issuer, Noncontrolled [Member] | Evelo Biosciences, Inc. [Member] | Investment Two [Member] |  |  |  |  |
Investments, fair value |  | 5,340 | 0 | 336 | 0
Purchases |  | 127 | 0 | 231 | 0
Reductions |  | (476) | 0 | (476) | 0
Transfers in/(out) at fair value |  | 0 | 11,496 | 0 | 11,496
Discount accretion |  | 0 | 11 | 0 | 11
Net unrealized appreciation (depreciation) on investments |  | (2,159) | (7,510) | 2,741 | (7,510)
Net realized gain (loss) on investments |  | 0 | 0 | 0 | 0
Investments, fair value |  | 2,832 | 3,997 | 2,832 | 3,997
Interest income |  |  | 415 | 0 | 415
Investment, Affiliated Issuer, Noncontrolled [Member] | Evelo Biosciences, Inc. [Member] | Investment Three [Member] |  |  |  |  |
Investments, fair value |  | 2,101 | 0 | 133 | 0
Purchases |  | 0 | 0 | 0 | 0
Reductions |  | (191) | 0 | (191) | 0
Transfers in/(out) at fair value |  | 0 | 4,612 | 0 | 4,612
Discount accretion |  | 0 | 5 | 0 | 5
Net unrealized appreciation (depreciation) on investments |  | (815) | (3,013) | 1,153 | (3,013)
Net realized gain (loss) on investments |  | 0 | 0 | 0 | 0
Investments, fair value |  | 1,095 | 1,604 | 1,095 | 1,604
Interest income |  |  | 166 | 0 | 166
Investment, Affiliated Issuer, Noncontrolled [Member] | Evelo Biosciences, Inc. [Member] | Investment Four [Member] |  |  |  |  |
Investments, fair value |  | 2,101 | 0 | 133 | 0
Purchases |  | 0 | 0 | 0 | 0
Reductions |  | (191) | 0 | (191) | 0
Transfers in/(out) at fair value |  | 0 | 4,598 | 0 | 4,598
Discount accretion |  | 0 | 3 | 0 | 3
Net unrealized appreciation (depreciation) on investments |  | (815) | (3,004) | 1,153 | (3,004)
Net realized gain (loss) on investments |  | 0 | 0 | 0 | 0
Investments, fair value |  | 1,095 | 1,597 | 1,095 | 1,597
Interest income |  |  | 163 | 0 | 163
Investment, Affiliated Issuer, Noncontrolled [Member] | Evelo Biosciences, Inc. [Member] | Investment Five [Member] |  |  |  |  |
Investments, fair value |  | 1,401 | 0 | 88 | 0
Purchases |  | 0 | 0 | 0 | 0
Reductions |  | (127) | 0 | (127) | 0
Transfers in/(out) at fair value |  | 0 | 3,067 | 0 | 3,067
Discount accretion |  | 0 | 4 | 0 | 4
Net unrealized appreciation (depreciation) on investments |  | (544) | (2,003) | 769 | (2,003)
Net realized gain (loss) on investments |  | 0 | 0 | 0 | 0
Investments, fair value |  | 730 | 1,068 | 730 | 1,068
Interest income |  |  | 114 | 0 | 114
Investment, Affiliated Issuer, Noncontrolled [Member] | Evelo Biosciences, Inc. [Member] | Investment Six [Member] |  |  |  |  |
Investments, fair value |  | 1,401 | 0 | 88 | 0
Purchases |  | 0 | 0 | 0 | 0
Reductions |  | (127) | 0 | (127) | 0
Transfers in/(out) at fair value |  | 0 | 3,067 | 0 | 3,067
Discount accretion |  | 0 | 4 | 0 | 4
Net unrealized appreciation (depreciation) on investments |  | (544) | (2,003) | 769 | (2,003)
Net realized gain (loss) on investments |  | 0 | 0 | 0 | 0
Investments, fair value |  | 730 | 1,068 | 730 | 1,068
Interest income |  |  | 111 | 0 | 111
Investment, Affiliated Issuer, Noncontrolled [Member] | Evelo Biosciences, Inc. [Member] | Investment Seven [Member] |  |  |  |  |
Investments, fair value |  |  | 0 | 132 | 0
Purchases |  |  | 0 | 0 | 0
Reductions |  |  | 0 | 0 | 0
Transfers in/(out) at fair value |  |  | 5,000 | 0 | 5,000
Discount accretion |  |  | 0 | 0 | 0
Net unrealized appreciation (depreciation) on investments |  |  | 3,485 | (132) | 3,485
Net realized gain (loss) on investments |  |  | 0 | 0 | 0
Investments, fair value |  | 0 | 8,485 | 0 | 8,485
Interest income |  |  | 0 | 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
Investment, Affiliated Issuer, Controlled [Member] |  |  |  |  |
Investments, fair value |  | 11,386 | 0 | 14,223 | 0
Purchases |  | 1,290 | 809 | 3,767 | 809
Reductions |  | (45) | 0 | (592) | 0
Transfers in/(out) at fair value |  | 6,716 | 10,818 | 7,179 | 10,818
Discount accretion |  | 3 | 3 | 10 | 3
Net unrealized appreciation (depreciation) on investments |  | 165 | 1,357 | (5,416) | 1,357
Net realized gain (loss) on investments |  | 0 | 0 | 0 | 0
Investments, fair value |  | 19,731 | 13,145 | 19,731 | 13,145
Interest income |  | 25 | 8 | 46 | 8
Interest Income, Operating, Paid in Kind |  | 216 | 158 | 560 | 158
Investment, Affiliated Issuer, Controlled [Member] | Investment [Member] |  |  |  |  |
Interest income |  | 241 | 166 | 606 | 166
Investment, Affiliated Issuer, Controlled [Member] | Better Place Forests Co. [Member] | Investment One [Member] |  |  |  |  |
Investments, fair value |  | 3,166 | 0 | 3,339 | 0
Purchases |  | 0 | 59 | 0 | 59
Reductions |  | 0 | 0 | 0 | 0
Transfers in/(out) at fair value |  | 0 | 1,759 | 0 | 1,759
Discount accretion |  | 2 | 2 | 6 | 2
Net unrealized appreciation (depreciation) on investments |  | (53) | 1,080 | (456) | 1,080
Net realized gain (loss) on investments |  | 0 | 0 | 0 | 0
Investments, fair value |  | 3,234 | 3,005 | 3,234 | 3,005
Interest income |  | 125 | 111 | 363 | 111
Interest Income, Operating, Paid in Kind |  | 119 | 105 | 345 | 105
Investment, Affiliated Issuer, Controlled [Member] | Better Place Forests Co. [Member] | Investment Two [Member] |  |  |  |  |
Investments, fair value |  | 1,549 | 0 | 1,630 | 0
Purchases |  | 0 | 0 | 0 | 0
Reductions |  | 0 | 0 | 0 | 0
Transfers in/(out) at fair value |  | 0 | 844 | 0 | 844
Discount accretion |  | 1 | 1 | 4 | 1
Net unrealized appreciation (depreciation) on investments |  | (26) | 536 | (222) | 536
Net realized gain (loss) on investments |  | 0 | 0 | 0 | 0
Investments, fair value |  | 1,583 | 1,434 | 1,583 | 1,434
Interest income |  | 63 | 55 | 184 | 55
Interest Income, Operating, Paid in Kind |  | 59 | 53 | 171 | 53
Investment, Affiliated Issuer, Controlled [Member] | Better Place Forests Co. [Member] | Investment Three [Member] |  |  |  |  |
Investments, fair value |  | 420 | 0 | 0 | 0
Purchases |  | 0 | 0 | 500 | 0
Reductions |  | 0 | 0 | 0 | 0
Transfers in/(out) at fair value |  | 0 | 2,061 | 0 | 2,061
Discount accretion |  | 0 | 0 | 0 | 0
Net unrealized appreciation (depreciation) on investments |  | 53 | 0 | (32) | 0
Net realized gain (loss) on investments |  | 0 | 0 | 0 | 0
Investments, fair value |  | 489 | 2,061 | 489 | 2,061
Interest income |  | 16 | 0 | 21 | 0
Interest Income, Operating, Paid in Kind |  | 16 | 0 | 21 | 0
Investment, Affiliated Issuer, Controlled [Member] | Better Place Forests Co. [Member] | Investment Four [Member] |  |  |  |  |
Investments, fair value |  | 415 | 0 | 0 | 0
Purchases |  | 0 | 750 | 500 | 750
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 |  | 53 | (259) | (33) | (259)
Net realized gain (loss) on investments |  | 0 | 0 | 0 | 0
Investments, fair value |  | 484 | 491 | 484 | 491
Interest income |  | 16 | 0 | 17 | 0
Interest Income, Operating, Paid in Kind |  | 16 | 0 | 17 | 0
Investment, Affiliated Issuer, Controlled [Member] | Better Place Forests Co. [Member] | Investment Five [Member] |  |  |  |  |
Investments, fair value |  | 0 |  | 0 |
Purchases |  | 500 |  | 500 |
Reductions |  | 0 |  | 0 |
Transfers in/(out) at fair value |  | 0 |  | 0 |
Discount accretion |  | 0 |  | 0 |
Net unrealized appreciation (depreciation) on investments |  | (32) |  | (32) |
Net realized gain (loss) on investments |  | 0 |  | 0 |
Investments, fair value |  | 474 |  | 474 |
Interest income |  | 6 |  | 6 |
Interest Income, Operating, Paid in Kind |  | 6 |  | 6 |
Investment, Affiliated Issuer, Controlled [Member] | Better Place Forests Co. [Member] | Investment Six [Member] |  |  |  |  |
Investments, fair value |  |  |  | 3,024 |
Purchases |  |  |  | 1,250 |
Reductions |  |  |  | 0 |
Transfers in/(out) at fair value |  |  |  | 0 |
Discount accretion |  |  |  | 0 |
Net unrealized appreciation (depreciation) on investments |  |  |  | (4,274) |
Net realized gain (loss) on investments |  |  |  | 0 |
Investments, fair value |  | 0 |  | 0 |
Interest income |  |  |  | 0 |
Interest Income, Operating, Paid in Kind |  |  |  | 0 |
Investment, Affiliated Issuer, Controlled [Member] | HIMV LLC [Member] |  |  |  |  |
Investments, fair value |  | 5,836 | 0 | 6,230 | 0
Purchases |  | 0 | 0 | 227 | 0
Reductions |  | (45) | 0 | (592) | 0
Transfers in/(out) at fair value |  | 0 | 6,154 | 463 | 6,154
Discount accretion |  | 0 | 0 | 0 | 0
Net unrealized appreciation (depreciation) on investments |  | 499 | 0 | (38) | 0
Net realized gain (loss) on investments |  | 0 | 0 | 0 | 0
Investments, fair value |  | 6,290 | 6,154 | 6,290 | 6,154
Interest income |  | 0 | 0 | 0 | 0
Interest Income, Operating, Paid in Kind |  | 0 | $ 0 | 0 | $ 0
Investment, Affiliated Issuer, Controlled [Member] | Nexii Building Solutions, Inc [Member] | Investment One [Member] |  |  |  |  |
Investments, fair value |  | 0 |  | 0 |
Purchases |  | 0 |  | 0 |
Reductions |  | 0 |  | 0 |
Transfers in/(out) at fair value |  | 6,716 |  | 6,716 |
Discount accretion |  | 0 |  | 0 |
Net unrealized appreciation (depreciation) on investments |  | (167) |  | (167) |
Net realized gain (loss) on investments |  | 0 |  | 0 |
Investments, fair value |  | 6,549 |  | 6,549 |
Interest income |  | 15 |  | 15 |
Interest Income, Operating, Paid in Kind |  | 0 |  | 0 |
Investment, Affiliated Issuer, Controlled [Member] | Nexii Building Solutions, Inc [Member] | Investment Two [Member] |  |  |  |  |
Investments, fair value |  | 0 |  | 0 |
Purchases |  | 790 |  | 790 |
Reductions |  | 0 |  | 0 |
Transfers in/(out) at fair value |  | 0 |  | 0 |
Discount accretion |  | 0 |  | 0 |
Net unrealized appreciation (depreciation) on investments |  | (162) |  | (162) |
Net realized gain (loss) on investments |  | 0 |  | 0 |
Investments, fair value |  | 628 |  | 628 |
Interest income |  | 0 |  | 0 |
Interest Income, Operating, Paid in Kind |  | $ 0 |  | $ 0 |
[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/1943274/2147477271/946-320-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_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_InvestmentIssuerNameAxis=hrzn_CadrenalTherapeuticsIncMember
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_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: |