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
 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%