Note 8 - Stock-based Compensation - Stock-based Compensation Expense (Details) - USD ($) $ in Thousands |
3 Months Ended | 6 Months Ended | ||
---|---|---|---|---|
Jun. 30, 2023 |
Jun. 30, 2022 |
Jun. 30, 2023 |
Jun. 30, 2022 |
|
Stock-based compensation expense | $ 1,628 | $ 1,444 | $ 2,895 | $ 3,018 |
Research and Development Expense [Member] | ||||
Stock-based compensation expense | 146 | 174 | 229 | 548 |
General and Administrative Expense [Member] | ||||
Stock-based compensation expense | $ 1,482 | $ 1,270 | $ 2,666 | $ 2,470 |