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Equity-based Compensation - Fair Value of Each Option Issued to Employees and Non-employees Estimated Using Black-Scholes 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]      
Options granted 2,182,773 2,832,784 2,209,597
Weighted-average exercise price $ 68.91 $ 39.16 $ 51.73
Weighted-average grant date fair value $ 42.28 $ 24.57 $ 33.82
Expected volatility 69.20% 68.90% 71.90%
Expected term (in years) 6 years 6 years 6 years
Risk-free interest rate 0.60% 2.20% 2.80%
Expected dividend yield 0.00% 0.00% 0.00%