Accrued Expenses (Details) - USD ($) $ in Thousands |
Mar. 31, 2016 |
Dec. 31, 2015 |
|---|---|---|
| Accrued expenses | ||
| Patent and license fees | $ 5,290 | $ 3,395 |
| Deferred initial public offering costs | 283 | |
| Employee compensation costs | 677 | 1,016 |
| Professional services | 1,048 | 382 |
| Other | 236 | 380 |
| Total | $ 7,251 | $ 5,456 |