Stock Plans - 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 |
|
| Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost | ||||
| Total stock-based compensation expense | $ 9 | $ 128 | $ 4 | $ 614 |
| Research and development | ||||
| Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost | ||||
| Total stock-based compensation expense | 0 | 0 | 0 | 91 |
| Selling, general and administrative | ||||
| Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost | ||||
| Total stock-based compensation expense | $ 9 | $ 128 | $ 4 | $ 523 |