Accounting Policies - Fair Value of Stock-Based Compensation Awards (Detail) |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract] | |||
| Volatility | 70.30% | 83.90% | 104.00% |
| Risk-free interest rate | 1.50% | 2.10% | 2.10% |
| Expected life of option | 6 years 2 months 5 days | 6 years 1 month 21 days | 6 years 1 month 2 days |
| Expected dividend yield | 0.00% | 0.00% | 0.00% |