Stockholders' Equity (Details 3) - 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 [Line Items] | ||||
| Employee Benefits and Share-based Compensation | $ 1,127 | $ 910 | $ 2,336 | $ 4,271 |
| Research and development | ||||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
| Employee Benefits and Share-based Compensation | 642 | 446 | 930 | 2,798 |
| General and administrative | ||||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
| Employee Benefits and Share-based Compensation | $ 485 | $ 464 | $ 1,406 | $ 1,473 |