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Stock Based Compensation (Details 2)	6 Months Ended
Stock Based Compensation (Details 2)	Jul. 31, 2012
Summary of assumptions used to estimate fair value of stock options granted
Expected volatility	36.21%
Risk-free interest rate	2.00%
Expected life in years	4 years 4 months 6 days

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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