Property, Plant and Equipment - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Depreciation and amortization expense	$ 329,000	$ 356,000	$ 1,043,000	$ 1,072,000
Amortization expense	8,000	$ 15,000	42,000	$ 50,000
Construction in progress	215,000		215,000		$ 198,000
Property, plant and equipment, Gross	32,778,000		32,778,000		32,710,000
Machinery, equipment and tooling
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Gross	21,193,000		21,193,000		21,146,000
Construction in progress (CIP) machinery & equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Gross	214,000		214,000		191,000
Construction in progress (CIP) building improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Gross	0		0		7,000
Construction in progress (CIP) IT equipment and software
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Gross	$ 1,000		$ 1,000		$ 0