Annual report pursuant to Section 13 and 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
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Expected term (years) 5 years 11 months 16 days 5 years 9 months 18 days 3 years 9 months 29 days
Volatility 86.00% 90.00% 94.00%
Risk-free interest rate 1.39% 1.64% 1.66%