Annual report pursuant to Section 13 and 15(d)

Stockholders' Equity (Deficit) - Additional Information (Detail)

v3.3.1.900
Stockholders' Equity (Deficit) - Additional Information (Detail) - USD ($)
 1 Months Ended 12 Months Ended
Jan. 21, 2016
Feb. 18, 2015
Aug. 01, 2014
Mar. 16, 2011
Oct. 05, 2009
Feb. 28, 2015
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Nov. 02, 2015
Class Of Warrant Or Right [Line Items]                    
Aggregate offering price of common stock which the Company may issue and sell     $ 30,000,000             $ 50,000,000
Proceeds from issuance of common stock and warrants, net of offering expenses   $ 28,100,000 $ 0       $ 28,883,000 $ 5,520,000 $ 2,392,000  
Aggregate commission rate on gross proceeds                   3.00%
Common stock sold, shares   8,300,000                
Warrants to purchase shares of common stock   8,300,000                
Initial exercise price of the warrants           $ 10.86        
Term of warrant           5 years        
Common stock sold, shares             71,462,059 62,898,233    
Reclassification of fair value from liability to permanent equity (deficit) of warrants exercised             $ 17,000 $ 10,116,000 $ 11,462,000  
Shares of common stock to be purchased with warrants             12,100,000      
Warrants                    
Class Of Warrant Or Right [Line Items]                    
Warrants exercised on a cashless basis               2,106,792 2,367,636  
Net proceeds from warrants exercised               $ 4,800,000 $ 1,900,000  
Common stock shares issued for cashless conversion of warrants               1,108,582 1,555,043  
Reclassification of fair value from liability to permanent equity (deficit) of warrants exercised               $ 10,100,000 $ 11,500,000  
Warrants exercised on cash basis               2,328,766 933,475  
March 2011 Offering                    
Class Of Warrant Or Right [Line Items]                    
Proceeds from issuance of common stock and warrants, net of offering expenses       $ 27,800,000            
Common stock sold, shares       14,313,081            
Common stock sold, price per share       $ 2.05            
Warrants exercisable, price per unit of warrant       $ 0.05            
Warrants issued       5,725,227            
Gross proceed from sale of common stock       $ 30,100,000            
Term of Warrants       5 years            
Warrant exercise price       $ 2.46            
Shares of common stock to be purchased with warrants             3,836,165 3,846,165    
October 2009 Offering                    
Class Of Warrant Or Right [Line Items]                    
Proceeds from issuance of common stock and warrants, net of offering expenses         $ 33,100,000          
Common stock sold, shares         18,324,599          
Common stock sold, price per share         $ 1.86          
Warrants exercisable, price per unit of warrant         $ 0.05          
Warrants issued         7,329,819          
Gross proceed from sale of common stock         $ 35,000,000          
Term of Warrants         5 years          
Warrant exercise price       $ 2.05            
October 2009 Offering | Warrants                    
Class Of Warrant Or Right [Line Items]                    
Change in fair value of common stock warrants               $ 1,300,000 $ 600,000  
October 2009 Offering | Scenario Previously Reported                    
Class Of Warrant Or Right [Line Items]                    
Warrant exercise price         $ 2.23          
August 2008 Offering | Warrants                    
Class Of Warrant Or Right [Line Items]                    
Change in fair value of common stock warrants                 2,400,000  
March 2011 Warrants | Warrants                    
Class Of Warrant Or Right [Line Items]                    
Change in fair value of common stock warrants             $ 3,900,000 $ 8,000,000 $ 500,000  
February 2015 Warrants                    
Class Of Warrant Or Right [Line Items]                    
Warrant exercise price   $ 10.86         $ 10.86      
Shares of common stock to be purchased with warrants   8,300,000         8,300,000      
February 2015 Warrants | Warrants                    
Class Of Warrant Or Right [Line Items]                    
Change in fair value of common stock warrants             $ 12,900,000      
Subsequent Event                    
Class Of Warrant Or Right [Line Items]                    
Exercise price of warrants adjusted $ 3.62                  
Minimum exercise price of warrants after adjustment date 3.62                  
Maximum exercise price of warrants after adjustment date 10.86                  
Company can force exercise of warrant if 20 day VWAP price exceeds $ 18.00