Consolidated Statements of Earnings - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Aug. 31, 2019	Aug. 31, 2018	Aug. 31, 2017
Income Statement [Abstract]
Operating revenues	$ 444,072	$ 547,705	$ 517,985
Cost of operating revenues	329,464	396,243	372,973
Gross profit	114,608	151,462	145,012
Operating expenses:
Selling expense	30,820	40,885	40,705
General and administrative expense	63,737	55,533	46,511
Engineering and research expense	13,936	16,032	17,147
Total operating expenses	108,493	112,450	104,363
Operating income	6,115	39,012	40,649
Other income (expense):
Interest expense	(4,767)	(4,687)	(4,757)
Interest income	2,402	1,640	1,178
Other expense, net	(1,643)	(2,112)	(1,355)
Earnings before income taxes	2,107	33,853	35,715
Income tax (benefit) expense	(65)	13,576	12,536
Net earnings	$ 2,172	$ 20,277	$ 23,179
Earnings per share:
Basic	$ 0.20	$ 1.89	$ 2.17
Diluted	$ 0.20	$ 1.88	$ 2.17
Shares used in computing earnings per share:
Basic	10,781	10,741	10,666
Diluted	10,810	10,772	10,694
Cash dividends declared per share	$ 1.24	$ 1.21	$ 1.17