Stock Plans (Details) - USD ($) $ in Thousands |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2018 |
Sep. 30, 2017 |
Sep. 30, 2018 |
Sep. 30, 2017 |
|
| Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] | ||||
| Total stock-based compensation expenses | $ 388 | $ 404 | $ 1,222 | $ 1,207 |
| Research and development [Member] | ||||
| Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] | ||||
| Total stock-based compensation expenses | 136 | 134 | 455 | 379 |
| General and administrative [Member] | ||||
| Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] | ||||
| Total stock-based compensation expenses | $ 252 | $ 270 | $ 767 | $ 828 |