|
Significant accounting policies (Details 5)
|
12 Months Ended |
|
Dec. 31, 2014
|
Dec. 31, 2013
|
Dec. 31, 2012
|
| Net loss per share |
|
|
|
| Potentially anti-dilutive securities excluded from calculation of diluted net loss per share (in shares) |
4,651,039 |
3,247,194 |
3,070,445 |
| Outstanding stock options |
|
|
|
| Net loss per share |
|
|
|
| Potentially anti-dilutive securities excluded from calculation of diluted net loss per share (in shares) |
4,206,440 |
2,388,062 |
1,424,241 |
| Restricted stock units |
|
|
|
| Net loss per share |
|
|
|
| Potentially anti-dilutive securities excluded from calculation of diluted net loss per share (in shares) |
293,747 |
529,850 |
899,204 |
| Outstanding warrants |
|
|
|
| Net loss per share |
|
|
|
| Potentially anti-dilutive securities excluded from calculation of diluted net loss per share (in shares) |
142,857 |
|
|
| Unvested restricted stock |
|
|
|
| Net loss per share |
|
|
|
| Potentially anti-dilutive securities excluded from calculation of diluted net loss per share (in shares) |
7,995 |
329,282 |
747,000 |