Income Taxes - Deferred Income Tax Assets and Liabilities (Detail) - USD ($)	Sep. 30, 2019	Sep. 30, 2018
Deferred Tax Assets:
Accrued liabilities and reserves	$ 344,000	$ 218,000
Allowance for doubtful accounts	104,000	71,000
Inventory	98,000	212,000
R&D tax credits carryforwards		87,000
Stock-based compensation	82,000	104,000
Net operating losses carryforwards	7,000	57,000
Gross Deferred Income Tax Assets	635,000	749,000
Deferred and Other Tax Liabilities:
Domestic international sales corporation	(464,000)	(543,000)
Percentage of completion	(2,048,000)	(1,717,000)
Property and equipment	(1,080,000)	(904,000)
Unrealized gain on investment	(265,000)	(75,000)
Unrecognized tax benefits	(150,000)	(150,000)
Gross Deferred and Other Income Tax Liabilities	(4,007,000)	(3,389,000)
Net Deferred and Other Income Tax Assets (Liabilities)	$ (3,372,000)	$ (2,640,000)