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Stockholders' Equity - Schedule of Weighted-Average Estimated Value of Employee Stock Options Granted (Detail)
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Equity [Abstract]    
Expected volatility 105.00% 155.00%
Risk-free interest rate 1.51% 0.70%
Expected dividends 0.00% 0.00%
Expected term in years 5 years 9 months 18 days 5 years 4 months 24 days