Stock-Based Compensation (Assumption To Value Stock Options) (Details)	3 Months Ended
Aug. 31, 2011
Non-Qualified Stock Options [Member]
Dividend yield	2.72%
Expected volatility	51.72%
Risk-free interest rate	2.13%
Expected term (years)	6.0
Market-Based Restricted Common Shares [Member]
Dividend yield	2.30%
Expected volatility	52.60%
Risk-free interest rate	1.76%
Modified expected term (years)	3

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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