Assumptions used in Estimating Fair Value of Warrant Derivative Liability (Detail) - $ / shares		6 Months Ended	12 Months Ended
	Sep. 15, 2016	Nov. 30, 2018	May 31, 2018
Fair value of underlying stock
Derivative [Line Items]
Fair value of underlying stock	$ 0.78	$ 0.58	$ 0.49
Risk free rate
Derivative [Line Items]
Risk free rate	1.20%	2.83%	2.63%
Expected Term (In Years)
Derivative [Line Items]
Expected term (in years)	5 years	2 years 9 months 14 days	3 years 3 months 18 days
Stock price volatility
Derivative [Line Items]
Stock price volatility	106.00%	62.00%	64.00%
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%	95.00%	50.00%
Probability of Holder Requesting Cash Payment
Derivative [Line Items]
Probability of holder requesting cash payment	50.00%	50.00%	50.00%