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Stockholders' Equity - Stock Options Valuation Assumptions (Detail)
3 Months Ended
Mar. 31, 2014
Mar. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Dividend yield 0.00% 0.00%
Minimum [Member]
   
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Risk-free interest rate 2.11% 0.41%
Expected volatility of common stock 63.54% 64.04%
Expected life of options 6 years 1 month 6 days 3 years
Maximum [Member]
   
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Risk-free interest rate 2.66% 0.63%
Expected volatility of common stock 65.03% 68.26%
Expected life of options 8 years 2 months 12 days 4 years 1 month 6 days