Stock-based Compensation - Fair Value of Stock Appreciation Rights Estimated, Black-Scholes Option Pricing Model (Detail) - Performance-Based Stock Appreciation Rights [Member] |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2015 |
Dec. 31, 2014 |
Dec. 31, 2013 |
|
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | |||
| Risk-free interest rate, Minimum | 1.35% | 1.77% | 0.91% |
| Risk-free interest rate, Maximum | 1.82% | 1.94% | 2.11% |
| Estimated volatility factor, Minimum | 62.70% | 64.81% | 67.60% |
| Estimated volatility factor, Maximum | 64.60% | 67.34% | 69.90% |
| Expected life (years) | 6 years | 6 years | |
| Minimum [Member] | |||
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | |||
| Expected life (years) | 5 years 6 months | ||
| Maximum [Member] | |||
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | |||
| Expected life (years) | 6 years | ||