Note 10 - Stock-based Compensation - Stock-based Compensation Expense (Details) - USD ($) $ in Thousands |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2020 |
Sep. 30, 2019 |
Sep. 30, 2020 |
Sep. 30, 2019 |
|
| Stock-based compensation expense | $ 1,104 | $ 1,326 | $ 3,340 | $ 3,779 |
| Cost of Sales [Member] | ||||
| Stock-based compensation expense | 25 | 68 | 98 | 197 |
| Research and Development Expense [Member] | ||||
| Stock-based compensation expense | 188 | 242 | 572 | 699 |
| Selling, General and Administrative Expenses [Member] | ||||
| Stock-based compensation expense | $ 891 | $ 1,016 | $ 2,670 | $ 2,883 |