Consolidated Statements of Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Treasury Stock [Member]	Capital In Excess Of Stated Value [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss, Net [Member]
Beginning balance, value at Aug. 31, 2017	$ 270,055	$ 18,780	$ (277,238)	$ 63,006	$ 477,615	$ (12,108)
Beginning balance, shares at Aug. 31, 2017		18,780	8,083
Net earnings	20,277	$ 0	$ 0	0	20,277	0
Other comprehensive loss	(5,980)	0	0	0	0	(5,980)
Total comprehensive income	14,297	0	0	0	0	0
Cash dividends per share	(13,006)	0	0	0	(13,006)	0
Issuance of common shares under share compensation plans, net	1,955	$ 61	0	1,894	0	0
Issuance of common shares under share compensation plans, net, shares		61
Share-based compensation expense	3,565	$ 0	0	3,565	0	0
Ending balance, value at Aug. 31, 2018	276,866	$ 18,841	$ (277,238)	68,465	484,886	(18,088)
Ending Balance, shares at Aug. 31, 2018		18,841	8,083
Net earnings	2,172	$ 0	$ 0	0	2,172	0
Other comprehensive loss	(1,234)	0	0	0	0	(1,234)
Total comprehensive income	938	0	0	0	0	0
Cash dividends per share	(13,375)	0	0	0	(13,375)	0
Issuance of common shares under share compensation plans, net	(947)	$ 29	0	(976)	0	0
Issuance of common shares under share compensation plans, net, shares		29
Share-based compensation expense	4,195	$ 0	0	4,195	0	0
Cumulative impact of ASC/ASU adoption | ASC 606 [Member]	532	0	0	0	532	0
Cumulative impact of ASC/ASU adoption | ASU 2018-02 [Member]	0	0	0	0	525	(525)
Ending balance, value at Aug. 31, 2019	268,209	$ 18,870	$ (277,238)	71,684	474,740	(19,847)
Ending Balance, shares at Aug. 31, 2019		18,870	8,083
Net earnings	38,629	$ 0	$ 0	0	38,629	0
Other comprehensive loss	(725)	0	0	0	0	(725)
Total comprehensive income	37,904	0	0	0	0	0
Cash dividends per share	(13,645)	0	0	0	(13,645)	0
Issuance of common shares under share compensation plans, net	434	$ 48	0	386	0	0
Issuance of common shares under share compensation plans, net, shares		48
Share-based compensation expense	5,616	$ 0	0	5,616	0	0
Ending balance, value at Aug. 31, 2020	$ 298,518	$ 18,918	$ (277,238)	$ 77,686	$ 499,724	$ (20,572)
Ending Balance, shares at Aug. 31, 2020		18,918	8,083