Note 12 - Share-based Compensation - Share-based Compensation Expense (Details) - USD ($) $ in Thousands |
3 Months Ended | |
|---|---|---|
Mar. 31, 2020 |
Mar. 31, 2019 |
|
| Total share-based compensation | $ 393 | $ 130 |
| Research and Development Expense [Member] | ||
| Total share-based compensation | 107 | 58 |
| General and Administrative Expense [Member] | ||
| Total share-based compensation | $ 286 | $ 72 |