Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Feb. 29, 2020	Feb. 28, 2019	Feb. 29, 2020	Feb. 28, 2019
Income Statement [Abstract]
Operating revenues	$ 113,788	$ 109,182	$ 223,181	$ 221,133
Cost of operating revenues	80,382	84,708	155,701	168,011
Gross profit	33,406	24,474	67,480	53,122
Operating expenses:
Selling expense	8,192	8,437	14,684	16,419
General and administrative expense	13,167	16,832	24,971	31,890
Engineering and research expense	3,405	3,665	6,907	7,233
Total operating expenses	24,764	28,934	46,562	55,542
Operating income (loss)	8,642	(4,460)	20,918	(2,420)
Other income (expense):
Interest expense	(1,191)	(1,178)	(2,377)	(2,383)
Interest income	389	751	1,004	1,405
Other (expense) income, net	(973)	(181)	(1,423)	11
Earnings (loss) before income taxes	6,867	(5,068)	18,122	(3,387)
Income tax expense (benefit)	1,351	(1,628)	4,261	(1,159)
Net earnings (loss)	$ 5,516	$ (3,440)	$ 13,861	$ (2,228)
Earnings (loss) per share:
Basic	$ 0.51	$ (0.32)	$ 1.28	$ (0.21)
Diluted	$ 0.51	$ (0.32)	$ 1.28	$ (0.21)
Shares used in computing earnings (loss) per share:
Basic	10,825	10,786	10,810	10,776
Diluted	10,857	10,786	10,843	10,776
Cash dividends declared per share	$ 0.31	$ 0.31	$ 0.62	$ 0.62