Quarterly report pursuant to Section 13 or 15(d)

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

v3.19.3
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%  
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%