Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Income Statement [Abstract]
Revenues	$ 118,716	$ 151,570	$ 225,291	$ 285,720
Cost of goods sold	101,563	121,885	189,867	234,209
Gross profit	17,153	29,685	35,424	51,511
Selling, general and administrative expenses	16,675	18,573	33,549	35,861
Research and development expenses	1,601	1,783	3,274	3,258
Amortization of intangible assets	44	44	88	88
Operating income (loss)	(1,167)	9,285	(1,487)	12,304
Interest expense	51	60	101	127
Interest income	(47)	(330)	(158)	(711)
Income (loss) before income taxes	(1,171)	9,555	(1,430)	12,888
Income tax provision (benefit)	(946)	2,134	(841)	2,692
Net income (loss)	$ (225)	$ 7,421	$ (589)	$ 10,196
Earnings (loss) per share:
Basic (in dollars per share)	$ (0.02)	$ 0.64	$ (0.05)	$ 0.88
Diluted (in dollars per share)	$ (0.02)	$ 0.64	$ (0.05)	$ 0.87
Weighted average shares:
Basic (in shares)	11,707	11,621	11,690	11,617
Diluted (in shares)	11,707	11,681	11,690	11,673
Dividends per share (in dollars per share)	$ 0.26	$ 0.26	$ 0.52	$ 0.52