Property, Plant and Equipment - Additional Information (Details) - USD ($)	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Depreciation and amortization expense	$ 1,442,000	$ 1,268,000
Depreciation	1,368,000	1,178,000
Amortization expense	74,000	90,000
Property, plant and equipment, Gross	32,710,000	32,050,000
Machinery, equipment and tooling
Property, Plant and Equipment [Line Items]
ROU assets	610,000	728,000
Property, plant and equipment, Gross	21,146,000	20,695,000
ATG
Property, Plant and Equipment [Line Items]
Construction in progress	198,000	$ 331,000
ATG \| Construction in progress (CIP) machinery & equipment and self-constructed assets
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Gross	191,000
ATG \| Construction in progress (CIP) computer equipment and software
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Gross	$ 7,000

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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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 of lessee's right to use underlying asset under operating lease.

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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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