Assumptions used in Estimating Fair Value of Warrant Derivative Liability (Detail) - $ / shares		3 Months Ended	12 Months Ended
	Sep. 15, 2016	Aug. 31, 2019	May 31, 2019
Grant Date Fair Value
Derivative [Line Items]
Fair value of underlying stock	$ 0.78	$ 0.40	$ 0.39
Risk Free Interest Rate
Derivative [Line Items]
Risk free rate	1.20%	1.50%	1.94%
Expected Term (In Years)
Derivative [Line Items]
Expected term (in years)	5 years	2 years 14 days	2 years 3 months 14 days
Stock Price Volatility
Derivative [Line Items]
Stock price volatility	106.00%	60.00%	61.00%
Expected Dividend Yield
Derivative [Line Items]
Expected dividend yield	0.00%	0.00%	0.00%
Probability of Fundamental Transaction
Derivative [Line Items]
Probability of fundamental transaction	50.00%	50.00%	50.00%
Probability of Holder Requesting Cash Payment
Derivative [Line Items]
Probability of holder requesting cash payment	50.00%	50.00%	50.00%