Annual report pursuant to Section 13 and 15(d)

Equity Awards - Stock Options and Other Equity Awards (Detail)

v3.22.2.2
Equity Awards - Stock Options and Other Equity Awards (Detail) - USD ($)
$ / shares in Units, $ in Thousands
 1 Months Ended 12 Months Ended
Apr. 30, 2022
Sep. 30, 2020
Jul. 31, 2020
Jan. 31, 2020
May 31, 2022
May 31, 2021
May 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Proceeds from stock option exercises         $ 390 $ 1,839 $ 5,602
Options outstanding, vested         9,900,000 12,800,000  
Options outstanding, nonvested         7,500,000 5,800,000  
Stock-based compensation     $ 1,600   $ 6,239 $ 10,429 $ 6,548
Issuance of common stock upon vesting of stock based compensation awards, shares           200,000  
Warrant exercises, shares         1,400,000 26,700,000  
Shares issued during the period new issues shares         7,900,000    
Stock option exercises, shares         500,000    
Maximum              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Stock options exercised, exercise price         $ 1.06    
Minimum              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Stock options exercised, exercise price         $ 0.63    
Common Stock              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Stock issued for bonuses and tendered for income tax, shares     300,000   2,582,000   380,000
Warrant exercises, shares         1,642,000 37,941,000 42,024,000
Stock option exercises, shares         510,000 2,591,000 8,723,000
Treasury Stock              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Stock issued for bonuses and tendered for income tax, shares     200,000       127,000
Management, Employees And Consultants [Member]              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Stock option granted, Shares         3,000,000.0    
Management, Employees And Consultants [Member] | Maximum              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Stock option granted, exercise price         $ 2.23    
Stock options grant date fair value         1.71    
Management, Employees And Consultants [Member] | Minimum              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Stock option granted, exercise price         0.43    
Stock options grant date fair value         $ 0.33    
Executives              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Stock option granted, Shares   3,350,000          
Percent of salary in lieu of cash, net of payroll deductions and withholding taxes 25.00%            
Shares issued         317,441    
Performance Shares [Member]              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Stock units granted, shares       11,700,000   4,350,000  
Stock units forfeited           3,900,000  
Issuance of common stock upon vesting of stock based compensation awards, shares         400,000    
Performance Shares [Member] | Executives              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Stock units granted, shares   4,350,000          
Award vesting period   3 years          
Stock Options | Management, Employees And Consultants [Member]              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Options term         10 years    
Award vesting period         3 years    
Restricted Stock Units (RSUs) [Member] | Executives              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Stock units granted, shares   1,120,000          
Award vesting period   3 years          
Issuance of common stock upon vesting of stock based compensation awards, shares         400,000