Quarterly report pursuant to Section 13 or 15(d)

Weighted Average Assumptions to Value Investor Warrants (Detail)

v3.19.3
Weighted Average Assumptions to Value Investor Warrants (Detail) - $ / shares
 3 Months Ended 12 Months Ended
Sep. 15, 2016
Aug. 31, 2019
May 31, 2019
Expected Term (In Years)      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Expected term 5 years 2 years 14 days 2 years 3 months 14 days
Risk Free Interest Rate      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Risk-free interest rate 1.20% 1.50% 1.94%
Grant Date Fair Value      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Grant-date fair value $ 0.78 $ 0.40 $ 0.39
Detachable Common Stock Warrants | Two Thousand And Nineteen Short Term Convertible Notes [Member] | Expected Dividend Yield      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Expected dividend yield     0.00%
Detachable Common Stock Warrants | Two Thousand And Nineteen Short Term Convertible Notes [Member] | Expected Term (In Years)      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Expected term     5 years
Detachable Common Stock Warrants | Minimum | Two Thousand And Nineteen Short Term Convertible Notes [Member] | Expected Dividend Yield      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Stock price volatility     55.80%
Detachable Common Stock Warrants | Minimum | Two Thousand And Nineteen Short Term Convertible Notes [Member] | Risk Free Interest Rate      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Risk-free interest rate     2.48%
Detachable Common Stock Warrants | Minimum | Two Thousand And Nineteen Short Term Convertible Notes [Member] | Grant Date Fair Value      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Grant-date fair value     $ 0.30
Detachable Common Stock Warrants | Maximum | Two Thousand And Nineteen Short Term Convertible Notes [Member] | Expected Dividend Yield      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Stock price volatility     55.88%
Detachable Common Stock Warrants | Maximum | Two Thousand And Nineteen Short Term Convertible Notes [Member] | Risk Free Interest Rate      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Risk-free interest rate     2.56%
Detachable Common Stock Warrants | Maximum | Two Thousand And Nineteen Short Term Convertible Notes [Member] | Grant Date Fair Value      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Grant-date fair value     $ 0.38