General form for registration of securities under the Securities Act of 1933

Convertible Instruments and Accrued Interest - Preferred stock (Details)

v3.26.1
Convertible Instruments and Accrued Interest - Preferred stock (Details)
$ / shares in Units, $ in Thousands
 9 Months Ended 12 Months Ended
Feb. 28, 2026
USD ($)
$ / shares
shares
May 31, 2025
USD ($)
$ / shares
shares
May 31, 2024
USD ($)
$ / shares
shares
Class of Stock      
Accrued dividends | $ $ 9,375 $ 8,269 $ 6,791
Accumulated deficit | $ $ (920,623) $ (887,786) $ (891,531)
Preferred stock, par value | $ / shares $ 0.001 $ 0.001 $ 0.001
Series B Convertible Preferred Stock      
Class of Stock      
Shares of preferred stock outstanding 19,000 19,000 19,000
Common stock conversion rate 10 10 10
Total shares of common stock if converted 190,000 190,000 190,000
Undeclared dividends | $ $ 28 $ 24 $ 19
Total shares of common stock if dividends converted 56,000 48,000 38,000
Undeclared dividend, shares   10  
Preferred stock dividend, value per share | $ / shares   $ 0.25  
Preferred stock conversion price, per share | $ / shares   0.5  
Preferred stock, liquidation preference per share ($ per share) | $ / shares $ 5 5  
Preferred stock, par value | $ / shares $ 0.001 $ 0.001 $ 0.001
Series C Convertible Preferred Stock      
Class of Stock      
Shares of preferred stock outstanding 6,000 6,000 6,000
Common stock conversion rate 2,000 2,000 2,000
Total shares of common stock if converted 12,670,000 12,670,000 12,670,000
Accrued dividends | $ $ 4,243 $ 3,769 $ 3,135
Total shares of common stock if dividends converted 8,486,000 7,538,000 6,270,000
Preferred stock conversion price, per share | $ / shares   $ 0.5  
Preferred stock, liquidation preference per share ($ per share) | $ / shares   $ 1,000  
Preferred stock dividend rate, as a percent   10.00%  
Preferred stock, par value | $ / shares $ 0.001 $ 0.001 $ 0.001
Fractional shares   0  
Series D Convertible Preferred Stock      
Class of Stock      
Shares of preferred stock outstanding 9,000 9,000 9,000
Common stock conversion rate 1,250 1,250 1,250
Total shares of common stock if converted 10,565,000 10,565,000 10,565,000
Accrued dividends | $ $ 5,132 $ 4,500 $ 3,656
Total shares of common stock if dividends converted 10,264,000 9,000,000 7,312,000
Preferred stock conversion price, per share | $ / shares   $ 0.8  
Preferred stock, liquidation preference per share ($ per share) | $ / shares   $ 1,000  
Preferred stock dividend rate, as a percent   10.00%  
Preferred stock, par value | $ / shares $ 0.001 $ 0.001 $ 0.001
Fractional shares   0