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Common Stock - Additional Information (Detail) - USD ($)
 1 Months Ended 12 Months Ended
May. 31, 2015
Apr. 30, 2015
Jul. 31, 2014
Oct. 31, 2013
Jun. 30, 2013
Dec. 31, 2012
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Class of Stock [Line Items]                  
Proceeds from issuance of common stock and warrants   $ 25,000,000 $ 20,000,000 $ 17,300,000          
Common stock issued in public offering   35,715,000 11,299,435 12,845,500          
Number of securities callable by each warrant or right warrants             1    
Exercise price of warrants   $ 0.85 $ 2.17 $ 1.80          
Warrant expiration period   5 years 13 months 5 years          
Proceeds from issuance of common stock $ 25,000,000           $ 26,324,565 $ 18,949,647 $ 23,491,597
Common stock, sold                 1,733,771
Sale of common stock and warrant, price per share     $ 1.77 $ 1.45         $ 1.91
Gross proceeds               $ 1,974,931 $ 530,097
Common stock, par value       $ 0.01     $ 0.01 $ 0.01  
Warrants termination agreement               2013-10  
Institutional Investors [Member]                  
Class of Stock [Line Items]                  
Proceeds from issuance of common stock         $ 3,000,000        
Shares available to sale         $ 30,000,000        
Exercise period of rights         3 years        
Additional amounts of common stock to sell         $ 27,000,000        
Warrants [Member]                  
Class of Stock [Line Items]                  
Number of shares of common stock or warrant in each unit sold to institutional investors     1 1          
Series A Warrants [Member]                  
Class of Stock [Line Items]                  
Number of securities callable by each warrant or right warrants             1    
Number of shares exercise               1,180,015  
Gross proceeds               $ 1,652,000  
Series A Warrants [Member]                  
Class of Stock [Line Items]                  
Gross proceeds                 $ 538,000
Number of warrants exercised                 384,534
Over-Allotment-Option [Member]                  
Class of Stock [Line Items]                  
Common stock issued in public offering 2,757,250 5,357,250              
Number of securities callable by warrants   4,017,938              
Warrants issued for purchase of additional common shares   4,017,938              
Common stock, price per share $ 0.699 $ 0.85              
Proceeds from issuance of common stock $ 1,800,000                
2012 Amended Sales Agreement [Member]                  
Class of Stock [Line Items]                  
Proceeds from issuance of common stock             $ 1,410,000 $ 285,000  
Percentage of compensation paid to sales agent             2.00%    
Shares available to sale           $ 30,000,000      
Common Stock [Member]                  
Class of Stock [Line Items]                  
Number of securities callable by each warrant or right warrants   0.75 0.85 0.5          
Number of securities callable by warrants               1,180,015  
Number of shares of common stock or warrant in each unit sold to institutional investors     1 1          
Number of shares issued upon warrants exercise                 384,534
Common Stock [Member] | Institutional Investors [Member]                  
Class of Stock [Line Items]                  
Common stock issued in public offering         329,131        
Common stock, sold         1,645,639        
Sale of stock, price per share         $ 1.823        
Common Stock [Member] | Series A Warrants [Member]                  
Class of Stock [Line Items]                  
Exercise price of warrants   $ 0.70              
Common Stock [Member] | 2012 Amended Sales Agreement [Member]                  
Class of Stock [Line Items]                  
Common stock, sold             2,546,681 193,271  
Sale of stock, price per share             $ 0.55 $ 1.47