Stockholders' Equity (Details 3) - USD ($) $ in Thousands |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2017 |
Jun. 30, 2016 |
Jun. 30, 2017 |
Jun. 30, 2016 |
|
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
| Employee Benefits and Share-based Compensation | $ 2,382 | $ 803 | $ 3,361 | $ 1,891 |
| Research and Development Expense [Member] | ||||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
| Employee Benefits and Share-based Compensation | 1,946 | 457 | 2,352 | 1,225 |
| General and Administrative Expense [Member] | ||||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
| Employee Benefits and Share-based Compensation | $ 436 | $ 346 | $ 1,009 | $ 666 |