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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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-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		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Depreciation and amortization expense	$ 339,000	$ 259,000	$ 902,000	$ 761,000
Amortization	18,000	$ 20,000	59,000	$ 57,000
Property, plant and equipment, Gross	31,583,000		31,583,000		$ 30,062,000
ATG
Property, Plant and Equipment [Line Items]
Construction in progress	597,000		597,000		$ 1,258,000
ATG \| Construction in progress (CIP) implementation costs
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Gross	267,000		267,000
ATG \| Construction in progress (CIP) IT equipment and software
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Gross	69,000		69,000
ATG \| Construction in progress (CIP) machinery & equipment and self-constructed assets
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Gross	$ 261,000		$ 261,000