Note 16 - Stock-based Compensation - Summary of Stock Option Weighted Average Assumptions, Employee Stock Purchase Plan (Details)	12 Months Ended
Aug. 31, 2019	Aug. 31, 2018	Aug. 31, 2017
Dividend yield	1.15%	1.32%	1.18%
The 2008 Employee Stock Purchase Plan [Member]
Risk-free interest rate	2.33%	1.55%	0.69%
Expected life (Year)	3 months	3 months	3 months
Expected volatility	10.89%	10.19%	8.60%
Dividend yield	1.12%	1.27%	1.25%

The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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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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- Definition

The risk-free interest rate assumption that is used in valuing an option on its own shares.

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Expected term of award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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