Quarterly report pursuant to Section 13 or 15(d)

Registered Direct Equity Offerings - Additional Information (Detail)

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Registered Direct Equity Offerings - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Millions
 6 Months Ended
Nov. 30, 2019
Sep. 30, 2019
Stockholders Equity Note [Line Items]    
Warrants to purchase common shares, shares   200,000
Class of warrants, exercise price   $ 0.45
Placement Agent    
Stockholders Equity Note [Line Items]    
Warrants to purchase common shares, shares 655,305  
Term of warrants 5 years  
Percentage of shares, issued as warrants 1.30%  
Placement Agent | Minimum    
Stockholders Equity Note [Line Items]    
Class of warrants, exercise price $ 0.40  
Placement Agent | Maximum    
Stockholders Equity Note [Line Items]    
Class of warrants, exercise price $ 0.444  
Subscription Agreements    
Stockholders Equity Note [Line Items]    
Number of shares to be sold 19,100,333  
Warrants to purchase common shares, shares 11,987,250  
Class of warrants, exercise price $ 0.45  
Term of warrants 5 years  
Proceeds from issuance of common shares $ 0  
Subscription Agreements | Minimum    
Stockholders Equity Note [Line Items]    
Purchase price, per share $ 0.30  
Subscription Agreements | Maximum    
Stockholders Equity Note [Line Items]    
Purchase price, per share $ 0.40