Note 13 - Share-based Compensation - Share-based Compensation Expense (Details) - USD ($) $ in Thousands |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2019 |
Jun. 30, 2018 |
Jun. 30, 2019 |
Jun. 30, 2018 |
|
| Total share-based compensation | $ 182 | $ 292 | $ 312 | $ 445 |
| Research and Development Expense [Member] | ||||
| Total share-based compensation | 67 | 81 | 125 | 103 |
| General and Administrative Expense [Member] | ||||
| Total share-based compensation | $ 115 | $ 211 | $ 187 | $ 342 |