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Common Stock Warrants - Additional Information (Detail) (USD $)
3 Months Ended 9 Months Ended 3 Months Ended 3 Months Ended 0 Months Ended 0 Months Ended
Sep. 30, 2014
Sep. 30, 2013
Jun. 30, 2013
Sep. 30, 2014
Sep. 30, 2013
Jun. 30, 2013
Warrant
Jan. 31, 2013
Warrant
Jun. 30, 2013
Before Modification
Jun. 30, 2013
After Modification
Jun. 30, 2013
Minimum
Before Modification
Jun. 30, 2013
Minimum
After Modification
Jun. 30, 2013
Maximum
Before Modification
Jun. 30, 2013
Maximum
After Modification
May 06, 2013
Class B Warrants
May 06, 2013
Class B Warrants
May 06, 2013
Class A-2 Warrants
May 06, 2013
Class A-2 Warrants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                  
Warrants to purchase shares of common stock             5,000                    
Exercise price of warrant             $ 2.65                    
Expected life       6 years 5 years 3 months 18 days 3 years       9 months 7 days 5 years 9 months 11 days 2 years 4 days 7 years 7 days        
Expected volatility of the underlying stock       114.00% 115.00% 87.00%                      
Risk-free interest rate       1.58% 1.17% 0.42%                      
Expected dividend rate       0.00% 0.00% 0.00%                      
Stock-based compensation expense $ 877,000 $ 1,808,000   $ 3,271,000 $ 3,276,000 $ 7,000                      
Warrants for purchase common stock shares     5,000,000                       4,000,000   1,000,000
Warrants exercisable life extended period                           5 years   5 years  
Expense related to extension of warrants     8,763,000                            
Volatility rate, minimum               77.00% 113.00%                
Volatility rate, maximum               96.00% 122.00%                
Risk free interest, minimum               0.11% 0.74%                
Risk free interest, maximum               0.22% 1.19%                
Expected dividend payment               $ 0 $ 0