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Note 14. Stock-Based Compensation (Detail) - Weighted Average Assumptions	3 Months Ended		6 Months Ended		12 Months Ended
	Feb. 29, 2012	Feb. 28, 2011	Feb. 29, 2012	Feb. 28, 2011	Aug. 31, 2011
Risk-free interest rate			0.94%		2.13%
Expected volatility			33.60%		31.10%
Dividend yield		1.25%	1.11%	1.25%	1.18%

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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