Assumptions used in Estimating Fair Value of Warrant Derivative Liability (Detail) - $ / shares		9 Months Ended	12 Months Ended
	Sep. 15, 2016	Feb. 29, 2020	May 31, 2019
Derivative [Line Items]
Expected dividend yield		0.00%
Grant Date Fair Value
Derivative [Line Items]
Fair value of underlying stock	$ 0.78	$ 1.05	$ 0.39
Risk Free Interest Rate
Derivative [Line Items]
Risk free rate	1.20%	0.93%	1.94%
Expected Term (In Years)
Derivative [Line Items]
Expected term (in years)	5 years	1 year 6 months 18 days	2 years 3 months 14 days
Stock Price Volatility
Derivative [Line Items]
Stock price volatility	106.00%	87.00%	61.00%
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%