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Stock-Based Compensation (Details 1)	12 Months Ended
Stock-Based Compensation (Details 1)	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2011
Stock-Based Compensation [Abstract]
Risk-free interest rate	1.10%	2.61%	2.79%
Expected volatility	74.10%	72.40%	71.51%
Expected dividend yield	0.00%	0.00%	0.00%
Expected term (in years)	5 years 6 months	5 years 6 months	5 years 6 months

The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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