Quarterly report pursuant to Section 13 or 15(d)

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

v3.7.0.1
Assumptions Used in Estimating Fair Value of Stock Options Granted (Detail) - 2002 Stock Incentive Plan
3 Months Ended
Mar. 31, 2017
Mar. 31, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Expected term 5 years 9 months 18 days 6 years 3 months 18 days
Volatility 79.43% 86.30%
Risk-free interest rate 1.98% 1.42%