|
Stockholders' Equity - Additional Information (Detail) (USD $)
In Millions, except Share data, unless otherwise specified |
3 Months Ended | 6 Months Ended | 3 Months Ended | 6 Months Ended | |||||
|---|---|---|---|---|---|---|---|---|---|
|
Jun. 30, 2014
|
Jun. 30, 2014
October 2009 Offering
|
Dec. 31, 2013
October 2009 Offering
|
Jun. 30, 2014
October 2009 Offering
Warrants
|
Jun. 30, 2014
October 2009 Offering
Warrants
|
Jun. 30, 2014
March 2011 Offering
|
Dec. 31, 2013
March 2011 Offering
|
Jun. 30, 2014
March 2011 Offering
Warrants
|
Jun. 30, 2014
March 2011 Offering
Warrants
|
|
| Class Of Warrant Or Right [Line Items] | |||||||||
| Warrants outstanding | 8,300,000 | 4,287,940 | 4,287,940 | 3,993,783 | 3,993,783 | ||||
| Warrants exercise price | 2.05 | 2.05 | 2.46 | 2.46 | |||||
| Change in fair value of common stock warrants | $ 3.4 | $ 3.1 | $ 3.2 | $ 5.0 | |||||