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Stock-Based Compensation (Details 2)	12 Months Ended
Stock-Based Compensation (Details 2)	Jan. 31, 2013	Jan. 31, 2012
Summary of assumptions used to estimate fair value of stock options granted
Risk-free interest rate	1.93%	2.57%
Expected volatility	35.51%	44.88%
Expected life	4 years 6 months 22 days	4 years 3 months 4 days
Dividend yield	0.00%	0.00%

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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