Business Description and Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Oct. 31, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for doubtful accounts	$ 142,000		$ 170,000
Inventory reserve	1,488,000		1,543,000
Interest paid	88,000	$ 80,000
Impairment of long-lived assets	0		0
Capitalised tooling				$ 143,000
Additional converted cost				$ 18,000
Warranty reserve	$ 420,000		428,000
Warranty period	27 years
Income taxes paid	$ 0	$ 875,000
Cumulative effect	20,319,000		$ 18,788,000
Other non-current assets
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Note receivable	$ 125,000