Loss Per Common Share - Securities Excluded from Computation of Earnings Per Share (Details) - shares shares in Thousands	12 Months Ended
	May 31, 2022	May 31, 2021	May 31, 2020
Stock options, warrants & unvested restricted stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	106,002	82,386	131,361
Convertible Debt Securities
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	12,000	18,000	3,864
Convertible Preferred Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	32,535	33,008	30,130