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Stockholders' Equity (Details 1)
12 Months Ended
Jan. 31, 2013
Jan. 31, 2012
Jan. 31, 2011
Expected volatility (range)   52.00%  
Expected volatility (range), Minimum 49.00%   51.00%
Expected volatility (range), Maximum 52.00%   53.00%
Weighted average volatility 52.00% 52.00% 53.00%
Risk-free interest rate   0.80%  
Weighted average interest rate 1.20% 0.80% 1.60%
Expected dividend yield 0.00% 0.00% 0.00%
Maximum [Member]
     
Expected term (in years) 7 years 5 years 5 years
Risk-free interest rate 1.20%   1.60%
Minimum [Member]
     
Expected term (in years) 3 years 4 years 4 years
Risk-free interest rate 0.70%   1.50%