Annual report pursuant to Section 13 and 15(d)

Private Securities Offerings - Additional Information (Detail)

v3.19.2
Private Securities Offerings - Additional Information (Detail) - USD ($)
 12 Months Ended
May 08, 2019
Mar. 23, 2018
Nov. 30, 2017
May 31, 2019
May 31, 2018
Jul. 26, 2019
May 14, 2019
Apr. 05, 2019
Feb. 13, 2019
Jun. 15, 2018
Nov. 24, 2017
Oct. 11, 2017
Sep. 08, 2017
May 31, 2017
Equity and Equity Units Offering Disclosure [Line Items]                            
Common stock, par value       $ 0.001                    
Warrants to purchase common shares, shares           1,984,769                
Common stock issued         $ 104,546                  
Share Price             $ 0.40              
Private Warrant Exchange [Member]                            
Equity and Equity Units Offering Disclosure [Line Items]                            
Common stock, par value $ 0.001                          
Warrants to purchase common shares, shares 7,541,279                          
Proceeds from issuance of common shares $ 3,000,000                          
Professional Fees $ 300,000                          
Share Price $ 0.40                          
Stock Issued During Period, Shares, Warrant Exercised 11,311,917                          
Noncash inducement interest expense $ 200,000                          
Private Warrant Exchange [Member] | Additional Shares [Member]                            
Equity and Equity Units Offering Disclosure [Line Items]                            
Warrants to purchase common shares, shares 3,770,638                          
Common Stock [Member]                            
Equity and Equity Units Offering Disclosure [Line Items]                            
Common stock sold at private equity offering         310,526                  
Common stock issued         $ 311                  
Offer To Amend And Exercise [Member]                            
Equity and Equity Units Offering Disclosure [Line Items]                            
Exercise price of warrants, per share                     $ 0.50      
Make Whole Securities [Member]                            
Equity and Equity Units Offering Disclosure [Line Items]                            
Common stock sold at private equity offering     503,015                      
Warrants to purchase common shares, shares     251,504                      
Make Whole Securities [Member] | Waiver And Subscription Agreement [Member]                            
Equity and Equity Units Offering Disclosure [Line Items]                            
Exercise price of warrants, per share                       $ 0.75 $ 1.00  
Purchase price, per share                       0.65 0.75  
Placement Agent                            
Equity and Equity Units Offering Disclosure [Line Items]                            
Exercise price of warrants, per share               $ 0.50 $ 0.50 $ 0.55        
Warrants to purchase common shares, shares               938,790 965,563 133,600        
Term of warrants               5 years 5 years 5 years        
Placement Agent | Make Whole Securities [Member]                            
Equity and Equity Units Offering Disclosure [Line Items]                            
Exercise price of warrants, per share     $ 0.715                      
Warrants to purchase common shares, shares       26,702                    
Term of warrants     5 years                      
Placement Agent | Make Whole Securities [Member] | Waiver And Subscription Agreement [Member]                            
Equity and Equity Units Offering Disclosure [Line Items]                            
Exercise price of warrants, per share                       $ 0.715 $ 0.825  
Private Equity Offering                            
Equity and Equity Units Offering Disclosure [Line Items]                            
Exercise price of warrants, per share       $ 0.75 $ 0.75                 $ 1.00
Warrant covering common stock shares purchased, percentage       50.00% 100.00%                  
Common stock sold at private equity offering       46,975,170 35,286,904                  
Common stock, par value       $ 0.001                    
Proceeds from private equity offering         $ 17,600,000                  
Term of warrants       5 years 5 years                  
Warrants to purchase common shares, shares       23,487,585 35,286,904                  
Proceeds from issuance of common shares       $ 23,500,000                    
Purchase price, per share         $ 0.50                  
Private Equity Offering | Placement Agent                            
Equity and Equity Units Offering Disclosure [Line Items]                            
Exercise price of warrants, per share       $ 0.50 $ 0.55                  
Warrants to purchase common shares, shares       4,446,917 2,813,491                  
Term of warrants       5 years 5 years                  
Professional Fees       $ 2,700,000                    
Private Equity Offering | Warrant Holders [Member] | Offer To Amend And Exercise [Member] | Common Stock [Member]                            
Equity and Equity Units Offering Disclosure [Line Items]                            
Common stock issued   $ 2,470,585                        
Private Equity Offering | Warrants                            
Equity and Equity Units Offering Disclosure [Line Items]                            
Exercise price of warrants, per share         $ 0.75                  
Warrants to purchase common shares, shares       23,487,585