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Note 10 - Stock-based Compensation (Details Textual) - USD ($) $ / shares in Units, $ in Thousands |  |  | 12 Months Ended |  |  |
--- | --- | --- | --- | --- | --- | ---
Aug. 26, 2021 | Apr. 25, 2019 | Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2020 | Dec. 31, 2022 | Jul. 01, 2021 | Mar. 31, 2016
Share Price (in dollars per share) |  |  | $ 2.69 | $ 5.24 |  |  |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Number (in shares) |  |  | 7,201,000 | 5,526,000 |  |  |  |
Share-Based Payment Arrangement, Expense |  |  | $ 8,314 | $ 7,660 |  |  |  |
Share-Based Payment Arrangement, Nonvested Award, Option, Cost Not yet Recognized, Amount |  |  | $ 4,500 |  |  |  |  |
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year) |  |  | 1 year 8 months 12 days |  |  |  |  |
The 2019 Stock Plan [Member] |  |  |  |  |  |  |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Expiration Period (Year) |  | 10 years |  |  |  |  |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized (in shares) |  |  |  |  |  |  | 4,558,621 |
Share-Based Compensation Arrangement by Share-Based Payment Award, Percentage Increase in Shares Available for Issuance Based on Common stock Outstanding | 4.00% |  |  |  |  |  |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Measurement Input, Shares (in shares) | 2,541,823 |  |  |  |  |  |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares) |  |  | 428,000 |  |  |  |  |
Share Price (in dollars per share) |  |  | $ 3.1 | $ 3.6 |  |  |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Number (in shares) |  |  | 7,201,000 | 5,526,000 |  | 4,694,000 |  |
The 2019 Stock Plan [Member] | Restricted Stock [Member] |  |  |  |  |  |  |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares) |  |  |  | 244,000 |  |  |  |
The 2019 Stock Plan [Member] | Restricted Stock [Member] | Director [Member] |  |  |  |  |  |  |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares) |  |  | 428,000 | 244,000 |  |  |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value (in dollars per share) |  |  | $ 3.1 | $ 3.75 |  |  |  |
The 2019 Stock Plan [Member] | Share-Based Payment Arrangement, Employee [Member] |  |  |  |  |  |  |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Number (in shares) |  |  | 1,800,000 | 1,300,000 |  |  |  |
The 2019 Stock Plan [Member] | Share-Based Payment Arrangement, Employee [Member] | Share-Based Payment Arrangement, Option [Member] |  |  |  |  |  |  |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Expiration Period (Year) |  |  |  |  | 10 years |  |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period (Year) |  |  |  |  | 3 years |  |  |
Inducement Equity Plan Options [Member] |  |  |  |  |  |  |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized (in shares) |  |  |  |  |  |  |  | 100,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Number (in shares) |  |  |  | 0 |  |  |  |

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