Condensed Consolidated Statements of Earnings - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Feb. 28, 2021	Feb. 29, 2020	Feb. 28, 2021	Feb. 29, 2020
Income Statement [Abstract]
Operating revenues	$ 143,577	$ 113,788	$ 252,062	$ 223,181
Cost of operating revenues	102,403	80,382	179,480	155,701
Gross profit	41,174	33,406	72,582	67,480
Operating expenses:
Selling expense	7,778	8,192	15,110	14,684
General and administrative expense	14,275	13,167	27,727	24,971
Engineering and research expense	3,312	3,405	6,402	6,907
Total operating expenses	25,365	24,764	49,239	46,562
Operating income	15,809	8,642	23,343	20,918
Other (expense) income:
Interest expense	(1,205)	(1,191)	(2,406)	(2,377)
Interest income	268	389	571	1,004
Other expense, net	(311)	(973)	(65)	(1,423)
Total other (expense) income	(1,248)	(1,775)	(1,900)	(2,796)
Earnings before income taxes	14,561	6,867	21,443	18,122
Income tax expense	2,685	1,351	2,472	4,261
Net earnings	$ 11,876	$ 5,516	$ 18,971	$ 13,861
Earnings per share:
Basic	$ 1.09	$ 0.51	$ 1.75	$ 1.28
Diluted	$ 1.08	$ 0.51	$ 1.74	$ 1.28
Shares used in computing earnings per share:
Basic	10,884	10,825	10,865	10,810
Diluted	10,981	10,857	10,934	10,843
Cash dividends declared per share	$ 0.32	$ 0.31	$ 0.64	$ 0.62