Quarterly report pursuant to Section 13 or 15(d)

Weighted Average Assumptions to Value Investor Warrants (Detail)

v3.10.0.1
Weighted Average Assumptions to Value Investor Warrants (Detail) - $ / shares
 3 Months Ended 12 Months Ended
Sep. 15, 2016
Aug. 31, 2018
May 31, 2018
Expected Term (In Years)      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Expected term 5 years 3 years 15 days 3 years 3 months 19 days
Risk Free Interest Rate      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Risk-free interest rate 1.20% 2.72% 2.63%
Grant Date Fair Value      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Grant-date fair value $ 0.78 $ 0.69 $ 0.49
Detachable Common Stock Warrants | Short-Term Convertible Notes | Expected Dividend Yield      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Expected dividend yield   0.00%  
Detachable Common Stock Warrants | Short-Term Convertible Notes | Stock Price Volatility      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Stock price volatility   69.80%  
Detachable Common Stock Warrants | Short-Term Convertible Notes | Expected Term (In Years)      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Expected term   5 years  
Detachable Common Stock Warrants | Minimum | Short-Term Convertible Notes | Risk Free Interest Rate      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Risk-free interest rate   1.77%  
Detachable Common Stock Warrants | Minimum | Short-Term Convertible Notes | Grant Date Fair Value      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Grant-date fair value   $ 0.30  
Detachable Common Stock Warrants | Maximum | Short-Term Convertible Notes | Risk Free Interest Rate      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Risk-free interest rate   1.93%  
Detachable Common Stock Warrants | Maximum | Short-Term Convertible Notes | Grant Date Fair Value      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Grant-date fair value   $ 0.39