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Fair Value of Stock Option Awards Using a Binomial Option-Pricing Model (Detail)
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Risk-free interest rate 2.02% 1.99% 3.49%
Expected volatility 75.30% 78.80% 78.80%
Expected dividend yield 0.00% 0.00% 0.00%
Expected term 5 years 5 years 5 years