Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity - Additional Information (Detail)

v2.4.0.8
Stockholders' Equity - Additional Information (Detail) (USD $)
In Millions, except Share data, unless otherwise specified
 3 Months Ended 3 Months Ended
Mar. 31, 2014
Mar. 31, 2014
October 2009 Offering [Member]
Dec. 31, 2013
October 2009 Offering [Member]
Mar. 31, 2014
October 2009 Offering [Member]
Warrants [Member]
Mar. 31, 2014
March 2011 Offering [Member]
Dec. 31, 2013
March 2011 Offering [Member]
Mar. 31, 2014
March 2011 Offering [Member]
Warrants [Member]
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       $ 0.3     $ (1.8)