Consolidated Statements Of Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Capital In Excess Of Stated Value [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive (Loss) Income, Net [Member]
Beginning balance, value at Aug. 31, 2015	$ 288,560	$ 18,684	$ 55,184	$ 458,903	$ (228,903)	$ (15,308)
Beginning balance, shares at Aug. 31, 2015		18,684,000			7,394,000
Net earnings	20,267			20,267
Other comprehensive income	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	688,790				689,000
Issuance of common shares under share compensation plans, value	$ (599)	$ 29	(628)
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	251,567	$ 18,713	57,338	466,926	$ (277,238)	(14,172)
Ending Balance, shares at Aug. 31, 2016		18,713,000			8,083,000
Net earnings	23,179			23,179
Other comprehensive income	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	$ 2,385	$ 67	2,318
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	270,055	$ 18,780	63,006	477,615	$ (277,238)	(12,108)
Ending Balance, shares at Aug. 31, 2017		18,780,000			8,083,000
Net earnings	20,277			20,277
Other comprehensive income	(5,980)					(5,980)
Total comprehensive income	14,297
Cash dividends per share	$ (13,006)			(13,006)
Repurchase of common stock, shares	0
Issuance of common shares under share compensation plans, value	$ 1,955	$ 61	1,894
Issuance of common shares under share compensation plans, shares		61,000
Share-based compensation expense	3,565		3,565
Ending balance, value at Aug. 31, 2018	$ 276,866	$ 18,841	$ 68,465	$ 484,886	$ (277,238)	$ (18,088)
Ending Balance, shares at Aug. 31, 2018		18,841,000			8,083,000