Stock-Based Compensation (Details 1)	12 Months Ended
Jan. 31, 2012 Y	Jan. 31, 2011 Y	Jan. 31, 2010 Y
Weighted average assumptions used for options granted
Risk-free interest rate	2.61%	2.79%	2.02%
Expected volatility	72.40%	71.51%	65.90%
Expected dividend yield	0.00%	0.00%	0.00%
Expected term (in years)	5.50	5.50	5.50

The period of time an equity-based award is expected to be outstanding. An equity-based award's expected term is generally determined based on, among other factors, the instrument's contractual term and the effects of employees' expected exercise and post-vesting employment termination behavior.

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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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