Annual report pursuant to Section 13 and 15(d)

Share-Based Compensation - Summary of Key Assumptions Used in Black-Scholes Option Pricing Model on Date of Grant for Options Granted to Non-Employees (Detail)

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Share-Based Compensation - Summary of Key Assumptions Used in Black-Scholes Option Pricing Model on Date of Grant for Options Granted to Non-Employees (Detail) - $ / shares
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Non Employee Stock Options [Member]    
Schedule Of Weighted Average Assumptions For Fair Values Of Stock Options [Line Items]    
Expected dividend yield    
Expected volatility 78.25% 73.79%
Risk-free interest rate 1.75% 1.09%
Expected life of option (years) 5 years 10 months 24 days 6 years 11 months 1 day
Weighted-average share price $ 0.26 $ 0.23
Weighted-average exercise price $ 0.52 $ 0.52
Model used Black-Scholes Black-Scholes
Stock Option [Member]    
Schedule Of Weighted Average Assumptions For Fair Values Of Stock Options [Line Items]    
Expected dividend yield 0.00%  
Joint Share Ownership Plan Awards [Member]    
Schedule Of Weighted Average Assumptions For Fair Values Of Stock Options [Line Items]    
Expected dividend yield 0.00%  
Expected volatility   76.00%
Risk-free interest rate   0.57%
Expected life of option (years)   3 years
Weighted-average share price   $ 0.17
Weighted-average exercise price   $ 0.17
Model used   Monte Carlo
Employee Stock Option [Member]    
Schedule Of Weighted Average Assumptions For Fair Values Of Stock Options [Line Items]    
Expected volatility 73.39% 77.00%
Risk-free interest rate 0.92% 0.49%
Expected life of option (years) 4 years 3 years 3 months
Weighted-average share price $ 0.29 $ 0.37
Weighted-average exercise price $ 1.22 $ 0.91
Model used Black-Scholes Black-Scholes