Quarterly report pursuant to Section 13 or 15(d)

Stock-Based Compensation - Weighted-Average Assumptions Used to Estimate Fair Value of Options Granted (Detail)

v3.5.0.2
Stock-Based Compensation - Weighted-Average Assumptions Used to Estimate Fair Value of Options Granted (Detail) - $ / shares
3 Months Ended 9 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2016
Sep. 30, 2015
Stock options        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Volatility 74.30% 55.71% 74.30% 61.16%
Risk free interest rate 1.17% 1.63% 1.17% 1.65%
Dividend yield 0.00% 0.00% 0.00% 0.00%
Term (years) 5 years 11 months 1 day 6 years 1 month 28 days 5 years 11 months 1 day 6 years 1 month 24 days
Weighted-average fair value of options granted during the period (usd per share) $ 1.30 $ 5.41 $ 1.30 $ 5.65
Non-Employee        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Volatility 72.97% 69.56% 74.50% 69.97%
Risk free interest rate 1.46% 2.02% 1.43% 2.11%
Dividend yield 0.00% 0.00% 0.00% 0.00%
Term (years) 7 years 7 months 21 days 8 years 6 months 29 days 7 years 10 months 21 days 8 years 10 months 2 days