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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
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Risk-free interest rate, Minimum 1.35% 1.77%
Risk-free interest rate, Maximum 1.82% 1.94%
Expected life (years) 6 years 6 years
Estimated volatility factor, Minimum 62.70% 64.81%
Estimated volatility factor, Maximum 64.60% 67.34%