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Note 1 - Organization (Details Textual) - USD ($) $ in Millions | Jun. 30, 2024 | Dec. 31, 2023 | Aug. 13, 2019
--- | --- | --- | ---
Debt Instrument, Face Amount | $ 715 | $ 615 |
Investment, Affiliated Issuer, Controlled [Member] | HIMV LLC [Member] | Co-lender [Member] |  |  |
Subsidiary, Ownership Percentage, Noncontrolling Owner | 30.00% |  |
Investment, Affiliated Issuer, Controlled [Member] | HIMV LLC [Member] | Co-lender [Member] |  |  |
Investment Owned, Net Assets, Percentage |  | 30.00% |
Horizon Technology Finance Corporation [Member] | Investment, Affiliated Issuer, Controlled [Member] | HIMV LLC [Member] |  |  |
Investment Owned, Net Assets, Percentage | 70.00% | 70.00% |
Asset-backed Notes 2019 [Member] |  |  |
Debt Instrument, Face Amount |  |  | $ 160
Asset-backed Notes 2019 [Member] | Affiliated Entity [Member] |  |  |
Debt Instrument, Face Amount |  |  | $ 100

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