Credit Arrangements (Narrative) (Details) - USD ($)	12 Months Ended
Aug. 31, 2020	Aug. 31, 2019
Debt Instrument [Line Items]
Long-term Debt	$ 116,344,000	$ 116,571,000
Elecsys Series 2006A Bonds [Member]
Debt Instrument [Line Items]
Long-term Debt	$ 1,344,000	1,571,000
Maturity date	Sep. 01, 2026
Effective interest rate	1.92%
Basis points	0.45%
Interest rate adjustment period	5 years
Elecsys Series 2006A Bond Adjusted Rate [Member]
Debt Instrument [Line Items]
Maturity date	Sep. 01, 2021
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Long-term Debt	$ 0	0
Maturity date	May 31, 2022
Unsecured revolving line of credit, maximum borrowing capacity outstanding	$ 50,000,000.0
Unsecured revolving line of credit, amount outstanding	0	0
Line of Credit Facility, Remaining Borrowing Capacity	$ 50,000,000.0
Effective interest rate	1.10%
Annual commitment fee	0.25%
Revolving Credit Facility [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Basis points	0.90%
Series A Senior Notes [Member]
Debt Instrument [Line Items]
Long-term Debt	$ 115,000,000	$ 115,000,000
Face amount	$ 115,000,000.0
Maturity date	Feb. 19, 2030
Interest rate	3.82%

Period after which adjustments can be made to the interest rate.

No definition available.

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- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

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- Definition

Face (par) amount of debt instrument at time of issuance.

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- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

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- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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- Definition

The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used.

+ References

No definition available.

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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

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- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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