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
 6 Months Ended 12 Months Ended
Sep. 15, 2016
Nov. 30, 2018
May 31, 2018
Expected Term (In Years)      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Expected term 5 years 2 years 9 months 14 days 3 years 3 months 18 days
Risk free rate      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Risk-free interest rate 1.20% 2.83% 2.63%
Fair value of underlying stock      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Grant-date fair value $ 0.78 $ 0.58 $ 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 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 | Fair value of underlying stock      
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 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 | Fair value of underlying stock      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Grant-date fair value   $ 0.39