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, 2018	$ 276,866	$ 18,841	$ (277,238)	$ 68,465	$ 484,886	$ (18,088)
Beginning balance, shares at Aug. 31, 2018		18,841	8,083
Net earnings	2,172	$ 0	$ 0	0	2,172	0
Other comprehensive income (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 income (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
Net earnings	42,572	$ 0	$ 0	0	42,572	0
Other comprehensive income (loss)	2,639	0	0	0	0	2,639
Total comprehensive income	45,211	0	0	0	0	0
Cash dividends per share	(14,166)	0	0	0	(14,166)	0
Issuance of common shares under share compensation plans, net	2,696	$ 73	0	2,623	0	0
Issuance of common shares under share compensation plans, net, shares		73
Share-based compensation expense	6,186	$ 0	0	6,186	0	0
Ending balance, value at Aug. 31, 2021	$ 338,445	$ 18,991	$ (277,238)	$ 86,495	$ 528,130	$ (17,933)
Ending Balance, shares at Aug. 31, 2021		18,991	8,083