Note 15 - Stock-based Compensation - Summary of Stock Option Weighted Average Assumptions of Employee Stock Options (Details) - $ / shares	3 Months Ended	9 Months Ended
May 31, 2017	May 31, 2016	May 31, 2017	May 31, 2016
Expected life (years) (Year)	7 years 146 days	7 years 182 days	7 years 146 days	7 years 255 days
Term structure of volatility
Dividend yield	1.18%	1.33%	1.18%	1.09%
Weighted average estimated fair value (in dollars per share)	$ 42.23	$ 40.57	$ 39.98	$ 46.05
Granted (in dollars per share)	$ 163.05	$ 152.10	$ 154.01	$ 168.51
Fair value as a percentage of exercise price	25.90%	26.70%	26.00%	27.30%
Minimum [Member]
Term structure of risk-free interest rate	0.49%	0.40%	0.07%	0.07%
Term structure of volatility	21.00%	24.00%	21.00%	21.00%
Maximum [Member]
Term structure of risk-free interest rate	1.89%	1.90%	2.09%	2.12%
Term structure of volatility	29.00%	30.00%	30.00%	30.00%

Discount rate from fair value on purchase date that participants pay for shares.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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- Definition

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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- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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- Definition

Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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No definition available.

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- Definition

Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(i)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.D.2)
-URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809

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