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Stock-Based Compensation - Fair Value of Options Granted, Determined, Using Weighted-Average Assumptions (Detail)
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Risk-free interest rate 1.23% 2.98% 2.62%
Expected term (years) 7 years 7 years 7 years
Expected stock price volatility 78.00% 46.00% 46.00%
Dividend yield 0.00% 1.41% 3.77%