Consolidated Statements of Earnings - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Aug. 31, 2020	Aug. 31, 2019	Aug. 31, 2018
Income Statement [Abstract]
Operating revenues	$ 474,692	$ 444,072	$ 547,705
Cost of operating revenues	322,149	329,464	396,243
Gross profit	152,543	114,608	151,462
Operating expenses:
Selling expense	31,444	30,820	40,885
General and administrative expense	52,947	63,737	55,533
Engineering and research expense	13,950	13,936	16,032
Total operating expenses	98,341	108,493	112,450
Operating income	54,202	6,115	39,012
Other (expense) income:
Interest expense	(4,759)	(4,767)	(4,687)
Interest income	1,956	2,402	1,640
Other expense, net	(2,556)	(1,643)	(2,112)
Total other (expense) income	(5,359)	(4,008)	(5,159)
Earnings before income taxes	48,843	2,107	33,853
Income tax expense (benefit)	10,214	(65)	13,576
Net earnings	$ 38,629	$ 2,172	$ 20,277
Earnings per share:
Basic	$ 3.57	$ 0.20	$ 1.89
Diluted	$ 3.56	$ 0.20	$ 1.88
Shares used in computing earnings per share:
Basic	10,823	10,781	10,741
Diluted	10,861	10,810	10,772
Cash dividends declared per share	$ 1.26	$ 1.24	$ 1.21