Property, Plant and Equipment - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Depreciation and amortization expense	$ 358,000	$ 363,000	$ 714,000	$ 718,000
Amortization expense	17,000	$ 17,000	34,000	$ 35,000
Construction in progress	167,000		167,000		$ 198,000
Property, plant and equipment, Gross	32,724,000		32,724,000		32,710,000
Machinery, equipment and tooling
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Gross	21,187,000		21,187,000		21,146,000
Construction in progress (CIP) machinery & equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Gross	160,000		160,000		191,000
Construction in progress (CIP) building improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Gross	6,000		6,000		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