Annual report pursuant to Section 13 and 15(d)

Stock Options and Warrants (Detail)

v3.20.2
Stock Options and Warrants (Detail) - USD ($)
 12 Months Ended
May 31, 2020
May 31, 2019
May 31, 2018
Stock option and warrant activity      
Options and warrants outstanding, Number of Shares 178,591,849 132,385,269  
Granted, Number of Shares 57,720,125 64,834,121  
Exercised, Number of Shares (101,852,619) (7,541,279)  
Forfeited/expired/cancelled, Number of Shares (3,098,826) (11,086,262)  
Options and warrants outstanding, Number of Shares 131,360,529 178,591,849 132,385,269
Outstanding exercisable, Number of Shares 131,357,234    
Options and warrants outstanding, Weighted Average Exercise Price $ 0.71 $ 0.80  
Granted, Weighted Average Exercise Price 0.47 0.57  
Exercised, Weighted Average Exercise Price 0.56 0.40  
Forfeited/expired/cancelled, Weighted Average Exercise Price 0.74 0.81  
Options and warrants outstanding, Weighted Average Exercise Price 0.65 $ 0.71 $ 0.80
Outstanding exercisable, Weighted Average Exercise Price $ 0.65    
Options and warrants outstanding, Weighted Average Remaining Contractual Life in Years 5 years 9 months 14 days 3 years 7 months 27 days 3 years 9 months 10 days
Outstanding exercisable, Weighted Average Remaining Contractual Life in Years 3 years 9 months 14 days    
Options and warrants outstanding, Aggregate Intrinsic Value $ 302,961,000 $ 896,400 $ 3,673
Outstanding exercisable, Aggregate Intrinsic Value $ 295,704,000