Annual report pursuant to Section 13 and 15(d)

Stock Plans and Stock-Based Compensation - Estimated Weighted-Average Grant Date Fair Value (Detail)

v3.3.1.900
Stock Plans and Stock-Based Compensation - Estimated Weighted-Average Grant Date Fair Value (Detail) - $ / shares
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]      
Expected term 6 years 1 month 6 days 6 years  
Expected volatility 78.00% 90.00%  
Risk-free interest rate 1.65% 2.02%  
Expected dividend yield 0.00% 0.00% 0.00%
Weighted-average grant date fair value per share $ 6.13 $ 4.06