Property, Plant and Equipment - Additional Information (Details) - USD ($)	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Depreciation and amortization expense	$ 356,000	$ 354,000
Depreciation	339,000	336,000
Amortization expense	17,000	$ 18,000
Construction in progress	179,000		$ 198,000
Property, plant and equipment, Gross	32,724,000		32,710,000
Machinery, equipment and tooling
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Gross	21,175,000		21,146,000
Construction in progress (CIP) machinery & equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Gross	173,000		191,000
Construction in progress (CIP) building improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Gross	5,000		7,000
Construction in progress (CIP) IT equipment and software
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Gross	$ 1,000		$ 0

The aggregate amount of recurring noncash expense charged against earnings in the period to allocate the cost of assets over their estimated remaining economic lives.

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Amount of structure or a modification to a structure under construction. Includes recently completed structures or modifications to structures that have not been placed into service.

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- Definition

The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.

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The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.

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Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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