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Share-Based Compensation - Schedule of Fair Value of Stock Option Award Granted Estimated on Date of Grant Using Black-Scholes-Merton Option Pricing Model (Detail) (USD $)
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Dividend yield         
Risk-free interest rate 0.60% 2.20% 2.50%
Weighted average volatility 68.40% 53.30% 52.40%
Expected life (in years) 5 years 2 months 12 days 5 years 6 months 5 years 9 months 18 days
Weighted average grant date fair value per share of options granted $ 4.10 $ 10.89 $ 14.95