Quarterly report pursuant to Section 13 or 15(d)

Private Warrant Exchange - Additional Information (Detail)

v3.20.1
Private Warrant Exchange - Additional Information (Detail) - USD ($)
 1 Months Ended 9 Months Ended
Feb. 28, 2020
Jan. 28, 2020
Dec. 30, 2019
Dec. 20, 2019
Jan. 31, 2020
Feb. 29, 2020
Feb. 28, 2019
Nov. 30, 2019
May 31, 2019
Class of warrants, exercise price               $ 0.45  
Common stock, par value           $ 0.001     $ 0.001
Proceeds From Exercise Of Warrants           $ 23,313,040 $ 0    
Private Warrant Exchange [Member]                  
Share Price     $ 0.50   $ 0.50        
Stock issued during period shares warrant exercise 8,626,745   2,676,000 4,690,000 4,448,000        
Common stock, par value $ 0.001   $ 0.001 $ 0.001 $ 0.001        
Proceeds From Exercise Of Warrants   $ 2,200,000 $ 1,100,000 $ 800,000 $ 1,900,000        
Noncash inducement interest expense $ 5,200,000                
Private Warrant Exchange [Member] | Additional Shares [Member]                  
Stock issued during period shares warrant exercise 784,245   446,000 1,340,000 408,000        
Private Warrant Exchange [Member] | Actual Shares [Member]                  
Stock issued during period shares warrant exercise 7,842,500   2,230,000 3,350,000 4,040,000        
Private Warrant Exchange [Member] | Maximum [Member]                  
Class of warrants, exercise price $ 0.75   $ 0.50 $ 0.75 $ 0.50        
Share Price 0.45     0.25          
Private Warrant Exchange [Member] | Minimum [Member]                  
Class of warrants, exercise price 0.30   $ 0.50 0.45 $ 0.50        
Share Price $ 0.18     $ 0.22