Summary of Significant Accounting Policies - Restricted Investments (Details) - USD ($) $ in Thousands	12 Months Ended
Aug. 31, 2020	Aug. 31, 2019	Aug. 31, 2018
Restricted Investments and Deferred Compensation
Restricted investments	$ 1,619	$ 1,260
Deferred compensation liabilities	1,629	1,275
Research and Product Development Costs
Research and development expense	4,007	4,021	$ 3,940
Stock Based Compensation
Stock-based compensation expense	$ 3,208	$ 2,176	$ 2,128
Weighted average assumptions used to estimate the fair value of options granted
Expected Dividend yield (as a percent)	0.70%	0.70%	0.90%
Expected life	6 years	6 years	6 years
Expected volatility (as a percent)	31.00%	31.40%	34.70%
Risk-free interest rate (as a percent)	1.40%	2.70%	1.90%

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Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Aggregate carrying value as of the balance sheet date of the liabilities for all deferred compensation arrangements payable beyond one year (or the operating cycle, if longer).

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The aggregate costs incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use.

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This element represents the noncurrent portion of investments which are not defined as or included in marketable (debt, equity, or other) securities that are pledged or subject to withdrawal restrictions.

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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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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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