Quarterly report pursuant to Section 13 or 15(d)

Stock Option and Incentive Plans - Assumptions to Compute Fair Value of Stock Option Grants (Detail)

v3.7.0.1
Stock Option and Incentive Plans - Assumptions to Compute Fair Value of Stock Option Grants (Detail) - USD ($)
3 Months Ended 6 Months Ended
Jun. 30, 2017
Jun. 30, 2016
Jun. 30, 2017
Jun. 30, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]        
Risk free interest rate 1.89% 1.28% 2.08% 1.22%
Expected dividend yield $ 0 $ 0 $ 0 $ 0
Expected term (in years) 5 years 6 months 14 days 5 years 5 months 23 days 6 years 4 years 11 months 15 days
Expected volatility 81.70% 80.70% 79.10% 79.90%