Stock Based Compensation Assumptions (Details) - USD ($) $ in Millions |
3 Months Ended | |
|---|---|---|
Mar. 31, 2016 |
Mar. 31, 2015 |
|
| Employees and directors | ||
| Assumptions | ||
| Risk free interest rate | 1.50% | 1.60% |
| Expected term | 6 years 3 months | 6 years 3 months |
| Expected volatility | 80.00% | 83.70% |
| Employees | ||
| Assumptions | ||
| Unrecognized stock-based compensation expense | $ 14.8 | |
| Period for recognition | 3 years 4 months 24 days | |
| Non-employees | ||
| Assumptions | ||
| Risk free interest rate | 1.90% | |
| Expected term | 10 years | |
| Expected volatility | 80.00% | |