Annual report pursuant to Section 13 and 15(d)

Stock Options and Warrants (Detail)

v3.10.0.1
Stock Options and Warrants (Detail) - USD ($)
 12 Months Ended
May 31, 2018
May 31, 2017
May 31, 2016
May 31, 2015
Stock option and warrant activity        
Options and warrants outstanding, Number of Shares 77,859,626 63,307,150 31,008,915  
Granted, Number of Shares 65,420,227 16,935,437 33,838,536  
Exercised, Number of Shares (6,322,263) (912,961) (1,050,301)  
Forfeited/expired/cancelled, Number of Shares (4,572,321) (1,470,000) (490,000)  
Options and warrants outstanding, Number of Shares 132,385,269 77,859,626 63,307,150 31,008,915
Outstanding exercisable, Number of Shares 128,872,852      
Options and warrants outstanding, Weighted Average Exercise Price $ 0.86 $ 0.83 $ 0.88  
Granted, Weighted Average Exercise Price 0.75 0.99 0.80  
Exercised, Weighted Average Exercise Price 0.50 0.55 0.70  
Forfeited/expired/cancelled, Weighted Average Exercise Price 0.94 1.56 2.01  
Options and warrants outstanding, Weighted Average Exercise Price 0.80 $ 0.86 $ 0.83 $ 0.88
Outstanding exercisable, Weighted Average Exercise Price $ 0.80      
Options and warrants outstanding, Weighted Average Remaining Contractual Life 3 years 9 months 11 days 3 years 4 months 24 days 3 years 2 months 12 days 2 years 11 months 9 days
Outstanding exercisable, Weighted Average Remaining Contractual Life 3 years 8 months      
Options and warrants outstanding, Aggregate Intrinsic Value $ 3,673 $ 40,250 $ 9,863,492 $ 5,538,335
Outstanding exercisable, Aggregate Intrinsic Value $ 3,673