Annual report pursuant to Section 13 and 15(d)

Fair Value of Warrants - Assumptions Used in Computing Fair Value of Derivative Warrants (Detail)

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Fair Value of Warrants - Assumptions Used in Computing Fair Value of Derivative Warrants (Detail)
Dec. 31, 2020
$ / shares
Oct. 28, 2020
$ / shares
Dec. 31, 2019
$ / shares
Jan. 09, 2019
$ / shares
Class of Warrant or Right [Line Items]        
Exercise price (usd per share) $ 104.18 $ 2.42   $ 7.43
2016 Offerings        
Class of Warrant or Right [Line Items]        
Exercise price (usd per share) $ 67.50   $ 67.50  
Expected life (years) 11 months 26 days   2 years 29 days  
Expected volatility | 2016 Offerings        
Class of Warrant or Right [Line Items]        
Measurement input assumption 1.4459   1.5069  
Risk-free interest rate | 2016 Offerings        
Class of Warrant or Right [Line Items]        
Measurement input assumption 0.0010   0.0158  
Expected dividend yield | 2016 Offerings        
Class of Warrant or Right [Line Items]        
Measurement input assumption 0.0000   0.0000