Annual report pursuant to Section 13 and 15(d)

Convertible Instruments and Accrued Interest - Preferred stock (Details)

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Convertible Instruments and Accrued Interest - Preferred stock (Details)
$ / shares in Units, $ in Thousands
 12 Months Ended
May 31, 2024
USD ($)
$ / shares
shares
May 31, 2023
USD ($)
$ / shares
shares
Class of Stock    
Accrued dividends | $ $ 6,791 $ 5,308
Preferred stock, par value | $ / shares $ 0.001 $ 0.001
Accumulated deficit | $ $ (891,531) $ (841,690)
Series B Convertible Preferred Stock    
Class of Stock    
Shares of preferred stock 19,000 19,000
Common stock conversion rate 10 10
Total shares of common stock if converted 190,000 190,000
Undeclared dividend | $ $ 19 $ 15
Total shares of common stock if dividends converted 38,000 30,000
Preferred Stock, Liquidation Preference Per Share | $ / shares $ 5.00  
Preferred stock dividend, value per share | $ / shares 0.25  
Preferred stock conversion price, per share | $ / shares 0.50  
Preferred stock, par value | $ / shares $ 0.001 $ 0.001
Undeclared dividend, shares 10  
Series C Convertible Preferred Stock    
Class of Stock    
Shares of preferred stock 6,000 6,000
Common stock conversion rate 2,000 2,000
Total shares of common stock if converted 12,670,000 12,670,000
Accrued dividends | $ $ 3,135 $ 2,500
Total shares of common stock if dividends converted 6,270,000 5,000,000
Preferred Stock, Liquidation Preference Per Share | $ / shares $ 1,000  
Preferred stock dividend rate, as a percent 10.00%  
Preferred stock conversion price, per share | $ / shares $ 0.50  
Preferred stock, par value | $ / shares $ 0.001 $ 0.001
Fractional shares 0  
Series D Convertible Preferred Stock    
Class of Stock    
Shares of preferred stock 9,000 9,000
Common stock conversion rate 1,250 1,250
Total shares of common stock if converted 10,565,000 10,565,000
Accrued dividends | $ $ 3,656 $ 2,808
Total shares of common stock if dividends converted 7,312,000 5,616,000
Preferred Stock, Liquidation Preference Per Share | $ / shares $ 1,000  
Preferred stock dividend rate, as a percent 10.00%  
Preferred stock conversion price, per share | $ / shares $ 0.80  
Preferred stock, par value | $ / shares $ 0.001 $ 0.001
Fractional shares 0