Quarterly report pursuant to Section 13 or 15(d)

Assumptions Used in Estimating Fair Value of Stock Options Granted (Detail)

v3.19.1
Assumptions Used in Estimating Fair Value of Stock Options Granted (Detail)
3 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions And Methodology [Abstract]    
Expected term 6 years 1 month 6 days 5 years 10 months 24 days
Volatility 86.20% 81.40%
Risk-free interest rate 2.64% 2.46%