Summary of Significant Accounting Policies - Effects of Adoption of 2014-09 (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018	Oct. 01, 2018	Sep. 30, 2018
Statement of Financial Position [Abstract]
Contract asset	$ 8,761		$ 8,761		$ 10,140	$ 0
Inventories, net	10,342		10,342		11,727	18,269
Contract liabilities (included within accrued liabilities)	0		0			0
Deferred income taxes	2,193		2,193			2,413
Retained earnings	38,114		38,114		40,695	37,097
Income Statement [Abstract]
Net sales	27,392	$ 27,794	56,458	$ 52,044
Cost of goods sold	25,304	25,265	51,633	47,487
Loss before income tax expense (benefit)	(1,224)	(2,035)	(3,020)	(3,186)
Net loss	$ (1,258)	$ (2,038)	$ (2,540)	$ (2,949)
Basic net loss per share (in dollars per share)	$ (0.23)	$ (0.37)	$ (0.46)	$ (0.53)
Diluted net loss per share (in dollars per share)	$ (0.23)	$ (0.37)	$ (0.46)	$ (0.53)
Income tax expense (benefit)	$ 34	$ 3	$ (480)	$ (237)
Previous Accounting Method
Statement of Financial Position [Abstract]
Contract asset	0		0			0
Inventories, net	14,931		14,931			18,269
Contract liabilities (included within accrued liabilities)	0		0
Deferred income taxes	2,193		2,193
Retained earnings	33,942		33,942			$ 37,097
Income Statement [Abstract]
Net sales	29,452		57,838
Cost of goods sold	27,622		53,586
Loss before income tax expense (benefit)	(1,482)		(3,593)
Net loss	$ (1,516)		$ (3,113)
Basic net loss per share (in dollars per share)	$ (0.27)		$ (0.56)
Diluted net loss per share (in dollars per share)	$ (0.27)		$ (0.56)
Accounting Standards Update 2014-09
Income Statement [Abstract]
Cost of goods sold			$ (333)
Accounting Standards Update 2014-09 | Effect of Accounting Change
Statement of Financial Position [Abstract]
Contract asset	$ 8,761		8,761		10,140
Inventories, net	(4,589)		(4,589)		(6,542)
Contract liabilities (included within accrued liabilities)	0		0
Deferred income taxes	0		0
Retained earnings	4,172		4,172		$ 3,598
Income Statement [Abstract]
Net sales	(2,060)		(1,380)
Cost of goods sold	(2,318)		(1,953)
Loss before income tax expense (benefit)	258		573
Net loss	$ 258		$ 573
Basic net loss per share (in dollars per share)	$ 0.04		$ 0.10
Diluted net loss per share (in dollars per share)	$ 0.04		$ 0.10