Stock Plans Stock-based compensation expense recorded for awards (Details) - USD ($) $ in Thousands |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2019 |
Sep. 30, 2018 |
Sep. 30, 2019 |
Sep. 30, 2018 |
|
| Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost | ||||
| Total stock-based compensation expense | $ 128 | $ 388 | $ 614 | $ 1,222 |
| Research and development | ||||
| Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost | ||||
| Total stock-based compensation expense | 0 | 136 | 91 | 455 |
| General and administrative [Member] | ||||
| Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost | ||||
| Total stock-based compensation expense | $ 128 | $ 252 | $ 523 | $ 767 |