Consolidated Statements Of Earnings - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Aug. 31, 2018	Aug. 31, 2017	Aug. 31, 2016
Income Statement [Abstract]
Operating revenues	$ 547,705	$ 517,985	$ 516,411
Cost of operating revenues	396,243	372,973	367,798
Gross profit	151,462	145,012	148,613
Operating expenses:
Selling expense	40,885	40,705	41,973
General and administrative expense	55,962	46,959	56,419
Engineering and research expense	16,052	17,147	15,846
Total operating expenses	112,899	104,811	114,238
Operating income	38,563	40,201	34,375
Other income (expense):
Interest expense	(4,687)	(4,757)	(4,751)
Interest income	1,640	1,178	645
Other (expense) income, net	(1,663)	(907)	(981)
Earnings before income taxes	33,853	35,715	29,288
Income tax expense	13,576	12,536	9,021
Net earnings	$ 20,277	$ 23,179	$ 20,267
Earnings per share:
Basic	$ 1.89	$ 2.17	$ 1.86
Diluted	$ 1.88	$ 2.17	$ 1.85
Shares used in computing earnings per share:
Basic	10,741	10,666	10,906
Diluted	10,772	10,694	10,930
Cash dividends declared per share	$ 1.21	$ 1.17	$ 1.13