Consolidated Statements Of Shareholders' Equity - USD ($) $ in Thousands	Common Stock [Member]	Capital In Excess Of Stated Value [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive (Loss) Income, Net [Member]	Total
Beginning balance, value at Aug. 31, 2014	$ 18,636	$ 52,866	$ 445,366	$ (132,020)	$ (2,201)	$ 382,647
Beginning balance, shares at Aug. 31, 2014	18,636,000			6,196,000
Net earnings			26,309			26,309
Other comprehensive income (loss)					(13,107)	(13,107)
Total comprehensive income						13,202
Cash dividends per share			(12,772)			(12,772)
Repurchase of common stock, value				$ (96,883)		$ (96,883)
Repurchase of common stock, shares				1,198,000		1,198,089
Issuance of common shares under share compensation plans, value	$ 48	(1,360)				$ (1,312)
Issuance of common shares under share compensation plans, shares	48,000
Excess tax benefits from share-based compensation		576				576
Share-based compensation expense		3,102				3,102
Ending balance, value at Aug. 31, 2015	$ 18,684	55,184	458,903	$ (228,903)	(15,308)	288,560
Ending Balance, shares at Aug. 31, 2015	18,684,000			7,394,000
Net earnings			20,267			20,267
Other comprehensive income (loss)					1,136	1,136
Total comprehensive income						21,403
Cash dividends per share			(12,244)			(12,244)
Repurchase of common stock, value				$ (48,335)		$ (48,335)
Repurchase of common stock, shares				689,000		688,790
Issuance of common shares under share compensation plans, value	$ 29	(628)				$ (599)
Issuance of common shares under share compensation plans, shares	29,000
Excess tax benefits from share-based compensation		(84)				(84)
Share-based compensation expense		2,866				2,866
Ending balance, value at Aug. 31, 2016	$ 18,713	57,338	466,926	$ (277,238)	(14,172)	251,567
Ending Balance, shares at Aug. 31, 2016	18,713,000			8,083,000
Net earnings			23,179			23,179
Other comprehensive income (loss)					2,064	2,064
Total comprehensive income						25,243
Cash dividends per share			(12,490)			$ (12,490)
Repurchase of common stock, shares						0
Issuance of common shares under share compensation plans, value	$ 67	2,318				$ 2,385
Issuance of common shares under share compensation plans, shares	67,000
Share-based compensation expense		3,350				3,350
Ending balance, value at Aug. 31, 2017	$ 18,780	$ 63,006	$ 477,615	$ (277,238)	$ (12,108)	$ 270,055
Ending Balance, shares at Aug. 31, 2017	18,780,000			8,083,000