Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Sep. 30, 2018
Deferred Tax Assets:
Net operating loss	$ 10,636	$ 13,444
Credit carryforwards	2,895	3,987
Deferred compensation	1,590	1,456
Uniform capitalization and inventory	983	1,043
Stock-based compensation	744	879
Reserve for accrued employee benefits	752	791
Warranty accrual	341	448
Accrued legal	115	154
Postretirement benefits liability	110	112
Goodwill	44	54
Other	276	112
Deferred tax assets	18,486	22,480
Deferred Tax Liabilities:
Depreciation and amortization	(5,138)	(6,946)
Deferred tax liabilities	(5,138)	(6,946)
Less: valuation allowance	(8,231)	(9,597)
Net deferred income tax asset	$ 5,117	$ 5,937