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Note 14. Stock-Based Compensation (Detail) - Weighted Average Assumptions (Non-Employee Directors' Stock Option Plan [Member])	9 Months Ended	12 Months Ended
	May 31, 2012	Aug. 31, 2011
Non-Employee Directors' Stock Option Plan [Member]
Risk-free interest rate	0.94%	2.13%
Expected life (in years)	5 years	5 years
Expected volatility	33.60%	31.10%
Dividend yield	1.11%	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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