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 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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-Publisher FASB
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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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Property, Plant and Equipment - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Depreciation and amortization expense	$ 363,000	$ 289,000	$ 718,000	$ 563,000
Amortization expense	17,000	$ 21,000	35,000	$ 41,000
Property, plant and equipment, Gross	32,643,000		32,643,000		$ 32,050,000
ATG
Property, Plant and Equipment [Line Items]
Construction in progress	442,000		442,000		331,000
ATG \| Construction in progress (CIP) machinery & equipment and self-constructed assets
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Gross	298,000		298,000		280,000
ATG \| Construction in progress (CIP) computer equipment and software
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Gross	27,000		27,000		32,000
ATG \| Construction in progress (CIP) building improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Gross	$ 117,000		$ 117,000		$ 19,000