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Stock-Based Compensation - Fair Value of Stock Appreciation Rights Estimated through Black-Scholes Option Pricing Model (Detail) (USD $)
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Share Based Payment Award Stock Options Valuation Assumptions [Line Items]      
Risk-free interest rate, Minimum 0.91% 0.11% 1.00%
Estimated volatility factor, Minimum 67.56% 71.18% 64.15%
Risk-free interest rate, Maximum 2.11% 1.41% 2.65%
Estimated volatility factor, Maximum 69.92% 74.34% 74.34%
Expected dividends         
Maximum [Member]
     
Share Based Payment Award Stock Options Valuation Assumptions [Line Items]      
Expected life (years) 6 years 6 years 6 years
Minimum [Member]
     
Share Based Payment Award Stock Options Valuation Assumptions [Line Items]      
Expected life (years) 5 years 6 months 5 years 6 months 5 years 6 months