Capital Stock - 2013 Lincoln Park Capital Fund, LLC Stock Purchase Agreement - Additional Information (Detail) - USD ($)
 1 Months Ended 6 Months Ended 12 Months Ended
Sep. 10, 2014
Aug. 06, 2014
Jun. 26, 2014
May. 29, 2014
Dec. 11, 2013
Jul. 19, 2013
Mar. 12, 2013
Jan. 22, 2013
Dec. 31, 2013
Jun. 30, 2015
Jun. 30, 2014
Dec. 31, 2014
Dec. 31, 2013
Sep. 30, 2014
Class of Stock [Line Items]                            
Number of shares of common stock sold 29,630 40,000 36,667 22,223     33,334 67,500            
Closing price of common stock                 $ 0.21       $ 0.21  
Proceeds from issuance of common stock $ 400,000 $ 600,000 $ 550,000 $ 500,000   $ 2,377,000 $ 1,000,000 $ 2,025,000     $ 2,638,000 $ 3,649,000 $ 6,538,000  
Previously Reported [Member]                            
Class of Stock [Line Items]                            
Number of shares of common stock sold 4,444,445 6,000,000 5,500,000 3,333,333     5,000,000 10,125,000            
Common Stock Purchase Agreement [Member]                            
Class of Stock [Line Items]                            
Potential number of shares of common stock to be sold                   67,556   10,133,334    
Number of shares of common stock sold                   $ 8,412,000   $ 8,412,000    
Lincoln Park Capital Fund, LLC [Member]                            
Class of Stock [Line Items]                            
Number of shares of common stock sold                   65,778     9,866,666  
Common stock sold                   $ 1,838,000     $ 1,838,000  
Lincoln Park Capital Fund, LLC [Member] | Common Stock Purchase Agreement [Member]                            
Class of Stock [Line Items]                            
Potential common stock value to be sold         $ 10,250,000       $ 10,250,000       $ 10,250,000  
Number of shares of common stock sold         11,112         0   8,200,000 1,666,666  
Common stock sold         $ 250,000             $ 1,588,000    
Cash fee paid for commitment to purchase additional shares         $ 155,000                  
Proceeds from issuance of common stock                       $ 1,588,000 $ 250,000  
Lincoln Park Capital Fund, LLC [Member] | Common Stock Purchase Agreement [Member] | Limit One [Member]                            
Class of Stock [Line Items]                            
Common shares authorized to purchase                   1,334       200,000
Lincoln Park Capital Fund, LLC [Member] | Common Stock Purchase Agreement [Member] | Limit Two [Member]                            
Class of Stock [Line Items]                            
Common shares authorized to purchase                   2,000       300,000
Lincoln Park Capital Fund, LLC [Member] | Common Stock Purchase Agreement [Member] | Limit Three [Member]                            
Class of Stock [Line Items]                            
Common shares authorized to purchase                   2,667       400,000
Lincoln Park Capital Fund, LLC [Member] | Common Stock Purchase Agreement [Member] | Minimum [Member]                            
Class of Stock [Line Items]                            
Closing price of common stock                   $ 7.50       $ 0.05
Common stock value under stock purchase agreement                   $ 500,000       $ 500,000
Lincoln Park Capital Fund, LLC [Member] | Common Stock Purchase Agreement [Member] | Previously Reported [Member]                            
Class of Stock [Line Items]                            
Number of shares of common stock sold         1,666,666