Annual report pursuant to Section 13 and 15(d)

Convertible Instruments and Accrued Interest - Preferred stock (Details)

v3.23.2
Convertible Instruments and Accrued Interest - Preferred stock (Details)
$ / shares in Units, $ in Thousands
 12 Months Ended
May 31, 2023
USD ($)
$ / shares
shares
May 31, 2022
USD ($)
$ / shares
shares
Class of Stock [Line Items]    
Accumulated deficit | $ $ (841,690) $ (766,131)
Accrued dividends | $ $ 5,308 $ 3,977
Preferred stock, par value | $ / shares $ 0.001 $ 0.001
Series B Convertible Preferred Stock    
Class of Stock [Line Items]    
Shares of preferred stock | shares 19,000 19,000
Common stock conversion rate 10 10
Total shares of common stock if converted | shares 190,000 190,000
Undeclared dividend | $ $ 15 $ 10
Total shares of common stock if dividends converted | shares 30,000 20,000
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 | shares 10,000  
Series C Convertible Preferred Stock    
Class of Stock [Line Items]    
Shares of preferred stock | shares 6,000 7,000
Common stock conversion rate 2,000 2,000
Total shares of common stock if converted | shares 12,670,000 13,806,000
Accrued dividends | $ $ 2,500 $ 2,014
Total shares of common stock if dividends converted | shares 5,000,000 4,028,000
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 | shares 0  
Series D Convertible Preferred Stock    
Class of Stock [Line Items]    
Shares of preferred stock | shares 9,000 9,000
Common stock conversion rate 1,250 1,250
Total shares of common stock if converted | shares 10,565,000 10,565,000
Accrued dividends | $ $ 2,808 $ 1,963
Total shares of common stock if dividends converted | shares 5,616,000 3,926,000
Preferred Stock, Liquidation Preference Per Share | $ / shares $ 1,000  
Preferred stock dividend rate, as a percent 10.00%  
Preferred stock dividend, value per share | $ / shares $ 0.50  
Preferred stock conversion price, per share | $ / shares 0.80  
Preferred stock, par value | $ / shares $ 0.001 $ 0.001
Fractional shares | shares 0