Annual report pursuant to Section 13 and 15(d)

Stock Options and Warrants - Additional Information (Detail)

v3.19.2
Stock Options and Warrants - Additional Information (Detail) - USD ($)
1 Months Ended 12 Months Ended
Apr. 05, 2019
Jan. 04, 2019
Apr. 16, 2019
May 31, 2019
May 31, 2018
May 31, 2017
Jul. 26, 2019
May 22, 2019
Feb. 13, 2019
Jul. 10, 2018
Jun. 15, 2018
Aug. 24, 2017
Mar. 31, 2016
Feb. 28, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                            
Stock option granted, Shares     150,000                      
Warrants to purchase common shares, shares             1,984,769              
Compensation expense       $ 3,388,095 $ 1,290,777 $ 1,204,791                
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number   1,145,834                        
Share-based Compensation Arrangement by Share-based Payment Award, Plan Modification, Description and Terms   150,000                        
Director                            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                            
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number                   100,000        
Placement Agent                            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                            
Warrants to purchase common shares, shares 938,790               965,563   133,600      
Term of warrants 5 years               5 years   5 years      
Exercise price of warrants, per share $ 0.50               $ 0.50   $ 0.55      
Consultant                            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                            
Warrants to purchase common shares, shares       300,000                    
Exercise price of warrants, per share       $ 0.56                    
Warrants grant date fair value       $ 0.30                    
Consultant | compensable warrant                            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                            
Warrants to purchase common shares, shares       500,000                    
Exercise price of warrants, per share       $ 0.51                    
Warrants grant date fair value       $ 0.28                    
Investor                            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                            
Warrants to purchase common shares, shares       1,000,000 5,000,000                  
Term of warrants         5 years                  
Exercise price of warrants, per share         $ 0.30                  
Investor | Series C Convertible Preferred Stock [Member]                            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                            
Warrants to purchase common shares, shares       3,895,000                    
Exercise price of warrants, per share       $ 0.50                    
Warrants grant date fair value       $ 0.50                    
Private Equity Offering                            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                            
Warrants to purchase common shares, shares       23,487,585 35,286,904                  
Exercise price of warrants, per share       $ 0.75 $ 0.75 $ 1.00                
Private Equity Offering | Placement Agent                            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                            
Warrants to purchase common shares, shares       4,446,917 2,813,491                  
Term of warrants       5 years 5 years                  
Exercise price of warrants, per share       $ 0.50 $ 0.55                  
Subscription Agreements                            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                            
Warrants to purchase common shares, shares                 5,364,240   1,970,000      
Term of warrants                 5 years          
Exercise price of warrants, per share                 $ 0.50   $ 0.75      
Convertible notes payable offering                            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                            
Stock option granted, Shares       5,460,000                    
Stock option granted, exerices price       $ 0.30                    
Stock options grant date fair value       $ 0.50                    
Warrants to purchase common shares, shares       $ 972,000                    
Direct equity offering                            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                            
Stock option granted, Shares 5,465,500                          
Stock options grant date fair value $ 0.50                          
Term of warrants 5 years                          
Direct equity offering | Placement Agent                            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                            
Stock option granted, exerices price $ 0.50                          
Term of warrants 5 years                          
Warrants to purchase common shares, shares $ 938,790                          
2012 Equity Incentive Plan                            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                            
Compensation expense       3,400,000 $ 1,300,000 $ 1,200,000                
Grant date fair value of options and warrants       2,100,000 $ 1,400,000 $ 900,000                
Unrecognized compensation expense       $ 4,300,000                    
Weighted average period over which unrecognized compensation expense is expected to be recognized       2 years 4 months 27 days                    
2012 Equity Incentive Plan | Employee Stock Option One | Director | Range One                            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                            
Stock option granted, Shares       1,219,726                    
Stock option granted, exerices price       $ 0.49                    
Vesting period       1 year                    
Stock options, term       10 years                    
2012 Equity Incentive Plan | Employee Stock Option One | Director | Range Two                            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                            
Stock option vested, Shares       0.57                    
2012 Equity Incentive Plan | Employee Stock Option One | Executive Management and Employees | Minimum                            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                            
Stock options grant date fair value       $ 0.26                    
2012 Equity Incentive Plan | Employee Stock Option One | Executive Management and Employees | Maximum                            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                            
Stock options grant date fair value       0.41                    
2012 Equity Incentive Plan | Employee Stock Option One | Managing Director | Range One                            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                            
Stock options grant date fair value       0.29                    
2012 Equity Incentive Plan | Employee Stock Option One | Managing Director | Range Two                            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                            
Stock options grant date fair value       $ 0.31                    
2012 Equity Incentive Plan | Stock Options                            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                            
Shares available for future stock-based grants       10,374,144                    
2012 Equity Incentive Plan | Stock Options | Before Amendment                            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                            
Shares available for future issuance               15,000,000       7,000,000 5,000,000 3,000,000
2012 Equity Incentive Plan | Stock Options | After Amendment                            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                            
Shares available for future issuance               25,000,000       15,000,000 7,000,000 5,000,000
2012 Equity Incentive Plan | Stock Options | Executive Management and Employees                            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                            
Stock option granted, Shares       3,715,000                    
Vesting period       3 years                    
Stock options, term       10 years                    
Warrants to purchase common shares, shares       950,000                    
2012 Equity Incentive Plan | Stock Options | Executive Management and Employees | Range One                            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                            
Stock option granted, exerices price       $ 0.48                    
2012 Equity Incentive Plan | Stock Options | Executive Management and Employees | Range Two                            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                            
Stock option granted, exerices price       $ 0.57