Note 2 - Significant Accounting Policies - Share-based Compensation Expense (Details) - USD ($) $ in Thousands |
12 Months Ended | |
---|---|---|
Dec. 31, 2023 |
Dec. 31, 2022 |
|
Share-based compensation expense | $ 3,262 | $ 5,062 |
Research and Development Expense [Member] | ||
Share-based compensation expense | 2,797 | 3,641 |
General and Administrative Expense [Member] | ||
Share-based compensation expense | $ 465 | $ 1,421 |