Consolidated Statements Of Earnings - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Aug. 31, 2017	Aug. 31, 2016	Aug. 31, 2015
Consolidated Statements Of Earnings [Abstract]
Operating revenues	$ 517,985	$ 516,411	$ 560,181
Cost of operating revenues	372,973	367,798	403,860
Gross profit	145,012	148,613	156,321
Operating expenses:
Selling expense	40,705	41,973	40,516
General and administrative expense	46,959	56,419	52,261
Engineering and research expense	17,147	15,846	12,849
Total operating expenses	104,811	114,238	105,626
Operating income	40,201	34,375	50,695
Interest expense	(4,757)	(4,751)	(2,626)
Interest income	1,178	645	631
Other expense, net	907	981	1,949
Earnings before income taxes	35,715	29,288	46,751
Income tax expense	12,536	9,021	20,442
Net earnings	$ 23,179	$ 20,267	$ 26,309
Earnings per share:
Basic	$ 2.17	$ 1.86	$ 2.23
Diluted	$ 2.17	$ 1.85	$ 2.22
Shares used in computing earnings per share:
Basic	10,666	10,906	11,818
Diluted	10,694	10,930	11,855
Cash dividends declared per share	$ 1.17	$ 1.13	$ 1.09