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Fair Value of Stock Options Under Black Scholes Option Pricing Model Based on Closing Stock Price on Date of Grant (Detail) (USD $)
3 Months Ended
Apr. 30, 2013
Mar. 31, 2013
Mar. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Exercise Price $ 0.21    
Stock option
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Exercise Price $ 0.41 $ 0 $ 0
Expected Term (in years) 4 years 7 months 2 days    
Volatility 26.00%    
Dividend rate 0.00%    
Interest rate 0.50%    
Stock option | Mr. Mark Meyers
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expected Term (in years) 3 years    
Volatility 17.40%    
Dividend rate 0.00%    
Interest rate 0.82%