Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity - Summary of Estimated Weighted-Average Assumptions (Detail)

v3.19.2
Stockholders' Equity - Summary of Estimated Weighted-Average Assumptions (Detail) - Employees - USD ($)
6 Months Ended
Jun. 30, 2019
Jun. 30, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Expected term (years) 5 years 10 months 24 days 4 years 7 months 6 days
Expected volatility 77.00% 73.50%
Risk-free interest rate 2.30% 2.60%
Expected dividend yield 0.00% 0.00%
Weighted-average estimated grant date fair value per share $ 21.82 $ 22.79
Options granted 1,750,825 1,578,750
Total estimated grant date fair value $ 38,203,000 $ 35,980,000