Annual report pursuant to Section 13 and 15(d)

Weighted Average Assumptions to Value Investor Warrants (Detail)

v3.19.2
Weighted Average Assumptions to Value Investor Warrants (Detail) - $ / shares
 6 Months Ended 12 Months Ended
Sep. 15, 2016
Sep. 15, 2016
Nov. 30, 2018
May 31, 2019
May 31, 2018
Expected Term (In Years)          
Fair Value Measurement Inputs and Valuation Techniques [Line Items]          
Expected term 5 years     2 years 3 months 14 days 3 years 3 months 18 days
Risk Free Interest Rate          
Fair Value Measurement Inputs and Valuation Techniques [Line Items]          
Risk-free interest rate 1.20%     1.94% 2.63%
Grant Date Fair Value          
Fair Value Measurement Inputs and Valuation Techniques [Line Items]          
Grant-date fair value   $ 0.78   $ 0.39 $ 0.49
Detachable Common Stock Warrants | Stock Price Volatility          
Fair Value Measurement Inputs and Valuation Techniques [Line Items]          
Stock price volatility     69.80%    
Detachable Common Stock Warrants | Expected Term (In Years)          
Fair Value Measurement Inputs and Valuation Techniques [Line Items]          
Risk-free interest rate     5.00%    
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 | 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 | Risk Free Interest Rate          
Fair Value Measurement Inputs and Valuation Techniques [Line Items]          
Risk-free interest rate     1.77%    
Detachable Common Stock Warrants | Minimum | Grant Date Fair Value          
Fair Value Measurement Inputs and Valuation Techniques [Line Items]          
Grant-date fair value     $ 0.30    
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 | Risk Free Interest Rate          
Fair Value Measurement Inputs and Valuation Techniques [Line Items]          
Risk-free interest rate     1.93%    
Detachable Common Stock Warrants | Maximum | Grant Date Fair Value          
Fair Value Measurement Inputs and Valuation Techniques [Line Items]          
Grant-date fair value     $ 0.39    
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