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 [Member]	Total
Beginning balance, value at Aug. 31, 2013	$ 18,571	$ 49,764	$ 405,580	$ (90,961)	$ (2,316)	$ 380,638
Beginning balance, shares at Aug. 31, 2013	18,571,000			5,698,000
Net earnings			51,512			51,512
Other comprehensive income (loss)					115	115
Total comprehensive income						51,627
Cash dividends per share			(11,726)			(11,726)
Repurchase of common stock, value				$ (41,059)		(41,059)
Repurchase of common stock, shares				498,000
Issuance of common shares under share compensation plans, value	$ 65	(1,639)				(1,574)
Issuance of common shares under share compensation plans, shares	65,000
Excess tax benefits from share-based compensation		722				722
Share-based compensation expense		4,019				4,019
Ending balance, value at Aug. 31, 2014	$ 18,636	52,866	445,366	$ (132,020)	(2,201)	382,647
Ending 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