Share Based Compensation (Summary Of Performance Stock Units Activity) (Details) (USD $)	12 Months Ended
Aug. 31, 2012	Aug. 31, 2011	Aug. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Beginning Balance	136,575	291,625
Grants	36,294
Vested		6,750	27,115
Forfeitures	2,983	1,350
Shares outstanding	146,298	136,575
Average exercised price beginning balance	$ 23.17	$ 23.23
Granted	$ 58.10
Forfeitures	$ 58.10	$ 24.33
Averaged exercised price ending balance	$ 30.97	$ 23.17
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Beginning Balance	98,625	87,701
Grants	19,386	27,932
Vested		(17,008)
Forfeitures	(38,987)
Shares outstanding	79,024	98,625
Average exercised price beginning balance	$ 42.21	$ 38.98
Granted	$ 57.09	$ 55.45
Vested		$ 47.27
Forfeitures	$ 43.30
Averaged exercised price ending balance	$ 45.32	$ 42.21
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Beginning Balance	71,826	75,093
Grants	40,212	40,699
Vested	37,381	40,337
Forfeitures	7,122	3,629
Shares outstanding	67,535	71,826
Average exercised price beginning balance	$ 47.99	$ 38.61
Granted	$ 58.27	$ 55.27
Vested	$ 47.87	$ 43.91
Forfeitures	$ 51.16	$ 51.17
Averaged exercised price ending balance	$ 54.35	$ 47.99

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The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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- Definition

Net number of share options (or share units) granted during the period.

+ References

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- Definition

The number of shares reserved for issuance under stock option agreements awarded under the plan that validly exist and are outstanding as of the balance sheet date, including vested options.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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- Definition

Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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As of the balance sheet date, the number of shares into which fully vested and expected to vest stock options outstanding can be converted under the option plan.

+ References

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As of the balance sheet date, the weighted-average exercise price for outstanding stock options that are fully vested or expected to vest.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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Weighted average price at which grantees can acquire the shares reserved for issuance on stock options awarded.

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