Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Schedule of Black-Scholes Option Pricing Model Assumptions (Detail)

v3.20.1
Summary of Significant Accounting Policies - Schedule of Black-Scholes Option Pricing Model Assumptions (Detail)
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 - Minimum 1.82% 2.55% 1.83%
Risk-free interest rate - Maximum 2.50% 3.03% 2.13%
Expected dividend yield 0.00% 0.00% 0.00%
Expected volatility - Minimum 105.00% 94.00% 93.00%
Expected volatility - Maximum 119.00% 100.00% 97.00%
Minimum [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expected term (in years) 5 years 6 months 5 years 6 months 5 years 6 months
Maximum [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expected term (in years) 6 years 1 month 6 days 6 years 1 month 6 days 6 years 1 month 6 days