Quarterly report pursuant to Section 13 or 15(d)

Assumptions used in Estimating Fair Value of Convertible Note Redemption Provision Derivative Liability (Detail)

v3.20.1
Assumptions used in Estimating Fair Value of Convertible Note Redemption Provision Derivative Liability (Detail)
 1 Months Ended 12 Months Ended
Jan. 30, 2019
yr
$ / shares
Nov. 15, 2018
yr
$ / shares
May 31, 2019
yr
$ / shares
Fair value of underlying stock      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Embedded derivative liability, price per share | $ / shares $ 0.49 $ 0.57  
Fair value of underlying stock | Note 1      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Embedded derivative liability, price per share | $ / shares     $ 0.39
Fair value of underlying stock | Note 2      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Embedded derivative liability, price per share | $ / shares     $ 0.39
Risk free rate      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Embedded Derivative Liability, Measurement Input 2.52 2.78  
Risk free rate | Note 1      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Embedded Derivative Liability, Measurement Input     2.21
Risk free rate | Note 2      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Embedded Derivative Liability, Measurement Input     1.95
Expected Term (In Years)      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Embedded derivative liability, expected term 2 years 1 year 7 months 9 days  
Expected Term (In Years) | Note 1      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Embedded derivative liability, expected term     1 year 25 days
Expected Term (In Years) | Note 2      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Embedded derivative liability, expected term     1 year 8 months 1 day
Stock price volatility      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Embedded Derivative Liability, Measurement Input 61 58.8  
Stock price volatility | Note 1      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Embedded Derivative Liability, Measurement Input     62.2
Stock price volatility | Note 2      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Embedded Derivative Liability, Measurement Input     62.2
Expected dividend yield      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Embedded derivative liability, dividend yield 0.00% 0.00%  
Expected dividend yield | Note 1      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Embedded derivative liability, dividend yield     0.00%
Expected dividend yield | Note 2      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Embedded derivative liability, dividend yield     0.00%
Discount factor      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Embedded Derivative Liability, Measurement Input 85 85  
Discount factor | Note 1      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Embedded Derivative Liability, Measurement Input     85
Discount factor | Note 2      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Embedded Derivative Liability, Measurement Input     85