Annual report pursuant to Section 13 and 15(d)

Convertible Instruments - Preferred stock (Detail)

v3.21.2
Convertible Instruments - Preferred stock (Detail) - USD ($)
 12 Months Ended
Jul. 30, 2020
Jan. 31, 2020
Aug. 29, 2019
May 31, 2021
May 31, 2020
Jan. 28, 2020
Oct. 11, 2019
Oct. 10, 2019
Class of Stock [Line Items]                
Preferred stock, shares authorized       5,000,000 5,000,000      
Preferred stock, par value       $ 0.001 $ 0.001      
Accrued dividends       $ 2,647,000 $ 981,000      
Common stock, shares authorized       800,000,000 800,000,000      
Series D Convertible Preferred Stock                
Class of Stock [Line Items]                
Preferred stock, shares authorized       11,737 12,000      
Preferred stock, par value   $ 0.001   $ 0.001 $ 0.001      
Preferred stock, shares issued       9,000 9,000      
Stock offering costs   $ 4,645            
Preferred stock, shares outstanding       8,452 8,452      
Preferred stock dividend rate, as a percent       10.00%        
Preferred stock dividend, value per share       $ 0.50        
Preferred stock, stated value per share       1,000        
Preferred stock conversion price, per share       $ 0.50        
Accrued dividends       $ 1,100,000 $ 300,000      
Accrued dividend, in shares of common stock       2,200,000 500,000      
Series C Convertible Preferred Stock                
Class of Stock [Line Items]                
Preferred stock, shares authorized       8,203 8,000 8,203 20,000 5,000
Preferred stock, par value       $ 0.001 $ 0.001      
Preferred stock, shares issued       8,000 8,000      
Stock offering costs     $ 200,000          
Preferred stock, shares outstanding       8,203 8,000      
Preferred stock dividend rate, as a percent       10.00%        
Preferred stock dividend, value per share       $ 0.50        
Preferred stock, stated value per share       1,000        
Preferred stock conversion price, per share       $ 0.50        
Accrued dividends       $ 1,500,000 $ 700,000      
Accrued dividend, in shares of common stock       3,000,000.0 1,400,000      
Series B Convertible Preferred Stock                
Class of Stock [Line Items]                
Preferred stock, shares authorized       400,000 400,000      
Preferred stock, par value       $ 0.001 $ 0.001      
Preferred stock, shares issued       79,000 92,000      
Preferred stock, shares outstanding       79,000 92,000      
Preferred stock dividend, value per share       $ 0.25        
Preferred stock, stated value per share       5.00        
Preferred stock conversion price, per share       $ 0.50        
Number of shares issued upon conversion       10        
Preferred stock cash dividend $ 200,000              
Undeclared dividend       $ 17,800 $ 200,000      
Undeclared dividend, shares       35,500 500,000