Stock-Based Awards - Fair Value of Stock Options Granted (Detail) |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2015 |
Dec. 31, 2014 |
Dec. 31, 2013 |
|
| Disclosure of Compensation Related Costs, Share-based Payments [Abstract] | |||
| Risk-free interest rate | 1.79% | 1.83% | 1.72% |
| Expected term (in years) | 6 years 4 days | 5 years 11 months 12 days | 5 years 11 months 23 days |
| Expected volatility | 74.20% | 79.40% | 79.70% |
| Expected dividend yield | 0.00% | 0.00% | 0.00% |