|
Stockholders' Equity - Additional Information (Detail) (USD $)
In Millions, except Share data, unless otherwise specified |
3 Months Ended | 3 Months Ended | 3 Months Ended | |||||||
|---|---|---|---|---|---|---|---|---|---|---|
|
Mar. 31, 2013
|
Mar. 31, 2013
August 2008 offering [Member]
|
Dec. 31, 2012
August 2008 offering [Member]
|
Mar. 31, 2013
August 2008 offering [Member]
Warrants [Member]
|
Mar. 31, 2013
October 2009 offering [Member]
|
Dec. 31, 2012
October 2009 offering [Member]
|
Mar. 31, 2013
October 2009 offering [Member]
Warrants [Member]
|
Mar. 31, 2013
March 2011 offering [Member]
|
Dec. 31, 2012
March 2011 offering [Member]
|
Mar. 31, 2013
March 2011 offering [Member]
Warrants [Member]
|
|
| Class of Warrant or Right [Line Items] | ||||||||||
| Warrants outstanding | 11,600,000 | 3,049,007 | 3,058,811 | 4,287,940 | 4,287,940 | 4,236,083 | 4,236,083 | |||
| Change in fair value of common stock warrants | $ 0.4 | $ 1.4 | $ 1.3 | |||||||