The following table is a reconciliation of the warrant liability measured at fair value using level 3 inputs (in thousands):
| Warrant Liability | ||||
|
Balance at December 31, 2011 |
$ | 9,209 | ||
|
Exercise of common stock warrants during 2012 |
(27,867 | ) | ||
|
Change in fair value of common stock warrants during 2012 |
51,216 | |||
|
|
|
|||
|
Balance at December 31, 2012 |
$ | 32,558 | ||