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Black-Scholes-Merton Option Pricing Model for Employee and Director Stock Options Granted (Detail) (USD $)
3 Months Ended
Mar. 31, 2014
Mar. 31, 2013
Share Based Payment Award Stock Options Valuation Assumptions [Line Items]    
Expected dividend yield 0.00% 0.00%
Weighted average expected volatility 66.00% 62.00%
Weighted average expected term (years) 5 years 10 months 6 days 6 years 11 days
Weighted average risk-free rate 1.79% 1.05%
Weighted average fair value per share $ 7.90 $ 2.25