Annual report pursuant to Section 13 and 15(d)

Quarterly Financial Data (Unaudited) - Summary of Quarterly Financial Data (Details)

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Quarterly Financial Data (Unaudited) - Summary of Quarterly Financial Data (Details) - USD ($)
 3 Months Ended 12 Months Ended 96 Months Ended
Jul. 31, 2016
Apr. 30, 2016
Jan. 31, 2016
Oct. 31, 2015
Jul. 31, 2015
Apr. 30, 2015
Jan. 31, 2015
Oct. 31, 2014
Jul. 31, 2016
Jul. 31, 2015
Jul. 31, 2016
Quarterly Financial Information Disclosure [Abstract]                      
Revenue      
Loss from operations (6,561,994) (6,251,119) (7,037,720) (7,035,219) (6,576,413) (5,986,286) (4,618,237) (4,060,206) $ (26,886,052) $ (21,241,142)  
Net loss (6,561,994) (6,251,409) (7,037,720) (7,037,391) (6,576,413) (5,987,345) (4,618,237) (4,061,116) $ (26,888,514) $ (21,243,111)  
Net loss applicable to common stockholders $ (6,561,994) $ (6,251,409) $ (7,037,720) $ (7,037,391) $ (6,576,413) $ (5,987,345) $ (4,618,237) $ (4,061,116)     $ (73,500,000)
Basic and diluted net loss per share $ 0.39 $ 0.37 $ 0.42 $ 0.47 $ 0.48 [1],[2] $ 0.48 [1],[2] $ 0.38 [1],[2] $ 0.33 [1],[2] $ (1.63) [3] $ (1.67) [3]  
[1] Loss per share is computed independently for each of the quarters presented. Therefore, the sum of the quarterly net loss per share will not necessarily equal the total for the year.
[2] Recast to reflect the 1-for-20 reverse stock split effected May 2015
[3] See Note 1, "Reverse Stock Split"