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Stock-Based Compensation - Schedule of Assumptions Used in Estimation of Fair Value of the Share-based Payment Awards on the Grant Date (Detail) - Options
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Risk-free interest rate   2.20%  
Risk-free interest rate, minimum 1.60%   1.60%
Risk-free interest rate, maximum 2.50%   1.80%
Volatility   109.50%  
Volatility, minimum 128.00%   70.20%
Volatility, maximum 138.50%   101.50%
Expected life (years)   4 years 4 years
Dividend yield 0.00% 0.00% 0.00%
Minimum      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Expected life (years) 3 years    
Maximum      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Expected life (years) 5 years