Annual report pursuant to Section 13 and 15(d)

Stockholders' Equity - Additional Information (Detail)

v2.4.0.8
Stockholders' Equity - Additional Information (Detail) (USD $)
12 Months Ended 0 Months Ended 12 Months Ended 0 Months Ended 12 Months Ended 12 Months Ended 12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Jan. 20, 2012
Oct. 29, 2010
Oct. 05, 2009
October 2009 Offering [Member]
Dec. 31, 2013
Warrants [Member]
Dec. 31, 2012
Warrants [Member]
Dec. 31, 2012
Common Stock [Member]
Dec. 31, 2011
Common Stock [Member]
Dec. 31, 2013
Common Stock [Member]
Oct. 29, 2010
Common Stock [Member]
Mar. 16, 2011
March 2011 Offering [Member]
Aug. 29, 2008
August 2008 Offering [Member]
Dec. 31, 2013
August 2008 Offering [Member]
Dec. 31, 2012
August 2008 Offering [Member]
Dec. 31, 2013
August 2008 Offering [Member]
Warrants [Member]
Dec. 31, 2012
August 2008 Offering [Member]
Warrants [Member]
Dec. 31, 2011
August 2008 Offering [Member]
Warrants [Member]
Dec. 31, 2013
Cashless Exercise of Warrants [Member]
Warrants [Member]
Dec. 31, 2012
Cashless Exercise of Warrants [Member]
Warrants [Member]
Dec. 31, 2013
October 2009 Offering [Member]
Dec. 31, 2012
October 2009 Offering [Member]
Dec. 31, 2013
October 2009 Offering [Member]
Warrants [Member]
Dec. 31, 2012
October 2009 Offering [Member]
Warrants [Member]
Dec. 31, 2011
October 2009 Offering [Member]
Warrants [Member]
Dec. 31, 2013
March 2011 Offering [Member]
Dec. 31, 2012
March 2011 Offering [Member]
Dec. 31, 2013
March 2011 Offering [Member]
Warrants [Member]
Dec. 31, 2012
March 2011 Offering [Member]
Warrants [Member]
Dec. 31, 2011
March 2011 Offering [Member]
Warrants [Member]
Class of Warrant or Right [Line Items]                                                              
Aggregate offering price of common stock which the Company may issue and sell $ 2,700,000     $ 15,000,000 $ 15,000,000                                                    
Aggregate commission rate on gross proceeds                       3.00%                                      
Common stock sold, shares 59,232,611 56,431,207       18,324,599     2,022,144 971,037 0   14,313,081 8,970,574                                  
Common stock sold, price per share           $ 1.86     $ 6.29 $ 2.66     $ 2.05 $ 2.04                                  
Net proceeds from sale of common stock   12,323,000 24,007,000     33,100,000     12,300,000 2,300,000     27,800,000 16,800,000                                  
Warrants exercisable, price per unit of warrant           $ 0.05             $ 0.05                                    
Warrants issued           7,329,819             5,725,227 3,588,221                                  
Gross proceed from sale of common stock           35,000,000             30,100,000 18,300,000                                  
Term of warrants           5 years             5 years 5 years                                  
Warrant exercise price           2.23             2.46                                    
Warrant, reduced exercise price           $ 2.05               $ 1.86                                  
Warrant, original exercise price                           $ 2.34                                  
Warrants exercised             933,475 4,060,538                       2,367,636 999,895                    
Net proceeds from warrants exercised 1,900,000 8,800,000                                                          
Common stock shares issued for cashless conversion of warrants                                       1,555,043 666,793                    
Reclassification of fair value from liability to permanent equity of warrants exercised 11,500,000 27,900,000                                                          
Warrants outstanding 8,300,000                           0 3,058,811           4,287,940 4,287,940       3,993,783 4,236,083      
Change in fair value of common stock warrants                                 $ 2,400,000 $ 9,900,000 $ 1,100,000         $ 600,000 $ 24,200,000 $ 1,400,000     $ 500,000 $ 17,100,000 $ 1,900,000