Quarterly report pursuant to Section 13 or 15(d)

Assumptions used in Estimating Fair Value of Warrant Derivative Liability (Detail)

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Assumptions used in Estimating Fair Value of Warrant Derivative Liability (Detail) - $ / shares
 3 Months Ended 12 Months Ended
Sep. 15, 2016
Aug. 31, 2018
May 31, 2018
Grant Date Fair Value      
Derivative [Line Items]      
Fair value of underlying stock $ 0.78 $ 0.69 $ 0.49
Risk Free Interest Rate      
Derivative [Line Items]      
Risk free rate 1.20% 2.72% 2.63%
Expected Term (In Years)      
Derivative [Line Items]      
Expected term (in years) 5 years 3 years 15 days 3 years 3 months 19 days
Stock Price Volatility      
Derivative [Line Items]      
Stock price volatility 106.00% 64.00% 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% 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%