Quarterly report pursuant to Section 13 or 15(d)

Common Stock - Additional Information (Detail)

v3.2.0.727
Common Stock - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended 6 Months Ended
May. 31, 2014
May. 07, 2014
May. 02, 2014
Dec. 11, 2013
Jun. 30, 2015
Jun. 30, 2014
Jun. 30, 2015
Jun. 30, 2014
Dec. 31, 2014
Mar. 31, 2014
Dec. 31, 2013
Dec. 31, 2011
Schedule of Capitalization, Equity [Line Items]                        
Common stock, par value         $ 0.001   $ 0.001   $ 0.001      
Common stock, shares authorized         125,000,000   125,000,000   125,000,000      
Common stock, shares issued         13,903,832   13,903,832   8,512,103      
Number of warrants issued to purchase common stock         14,033   14,033   14,033      
Exercise price of warrants $ 0.20                      
Exercise of common stock warrants 275,687 275,687                    
Fair value of common stock warrant derivative liabilities                   $ 9,998 $ 12,200  
Warrant derivative liability reclassified to additional paid-in capital     $ 2,701                  
Fair value adjustment of long term derivative liability           $ 7,297   $ 10,442        
Common Stock Warrant [Member]                        
Schedule of Capitalization, Equity [Line Items]                        
Fair value adjustment of long term derivative liability         $ 0 $ 7,297 $ 0 $ 10,405        
2011-2012 Notes [Member]                        
Schedule of Capitalization, Equity [Line Items]                        
Number of warrants issued to purchase common stock                       26,000
Exercise price of warrants                       $ 0.20
June 2013 Note and Warrant Agreement [Member]                        
Schedule of Capitalization, Equity [Line Items]                        
Number of warrants issued to purchase common stock       88,987                
Exercise price of warrants       $ 0.20                
Warrants exercisable date       Jun. 28, 2018                
Series D-2 Purchase Agreement [Member]                        
Schedule of Capitalization, Equity [Line Items]                        
Number of warrants issued to purchase common stock       87,532                
Exercise price of warrants       $ 0.20                
Warrants exercisable date       Dec. 11, 2018                
Increase in the shares of common stock underlying the warrants issued       54,120                
Revised number of common shares underlying the warrants issued       80,120