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Share Based Compensation - Schedule of Fair Value of Stock Option Award Granted Estimated on Date of Grant Using the Black-Scholes-Merton Option Pricing Model (Detail) (USD $)
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]      
Dividend yield         
Risk-free interest rate 1.10% 0.60% 2.20%
Weighted average volatility 64.60% 68.40% 53.30%
Expected life (in years) 5 years 7 months 6 days 5 years 2 months 12 days 5 years 6 months
Weighted average grant date fair value per share of options granted $ 1.47 $ 4.10 $ 10.89