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Stockholder's Equity (Deficit) - Summary of Weighted Average Assumptions Used in Black-Sholes Option-pricing Model (Detail) - $ / shares
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]      
Common stock value (per share) $ 21.81 $ 26.97 $ 20.65
Expected volatility 46.59% 48.13% 48.69%
Risk- free interest rate 0.65% 2.06% 2.88%
Expected life (years) 7 years 7 years 7 years
Forfeiture rate 0.00% 0.00% 0.00%
Dividend rate 0.00% 0.00% 0.00%