Consolidated Statements of Earnings - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Aug. 31, 2021	Aug. 31, 2020	Aug. 31, 2019
Income Statement [Abstract]
Operating revenues	$ 567,646	$ 474,692	$ 444,072
Cost of operating revenues	417,441	322,149	329,464
Gross profit	150,205	152,543	114,608
Operating expenses:
Selling expense	30,816	31,444	30,820
General and administrative expense	51,923	52,947	63,737
Engineering and research expense	13,359	13,950	13,936
Total operating expenses	96,098	98,341	108,493
Operating income	54,107	54,202	6,115
Other (expense) income:
Interest expense	(4,751)	(4,759)	(4,767)
Interest income	1,083	1,956	2,402
Other expense, net	(53)	(2,556)	(1,643)
Total other (expense) income	(3,721)	(5,359)	(4,008)
Earnings before income taxes	50,386	48,843	2,107
Income tax expense (benefit)	7,814	10,214	(65)
Net earnings	$ 42,572	$ 38,629	$ 2,172
Earnings per share:
Basic	$ 3.91	$ 3.57	$ 0.20
Diluted	$ 3.88	$ 3.56	$ 0.20
Shares used in computing earnings per share:
Basic	10,886	10,823	10,781
Diluted	10,985	10,861	10,810
Cash dividends declared per share	$ 1.30	$ 1.26	$ 1.24