Property, Plant and Equipment (Details) - USD ($)	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Property, Plant and Equipment
Gross property, plant, and equipment	$ 193,507,000		$ 191,322,000
Less accumulated depreciation and amortization, including accumulated amortization of finance leases	(110,565,000)		(109,008,000)
Property, plant, and equipment - net	82,942,000		82,314,000
Depreciation	2,707,000	$ 2,772,000
Asset impairment	0	$ 0
Land
Property, Plant and Equipment
Gross property, plant, and equipment	11,041,000		11,076,000
Improvements to land and leaseholds
Property, Plant and Equipment
Gross property, plant, and equipment	17,172,000		17,172,000
Buildings
Property, Plant and Equipment
Gross property, plant, and equipment	34,619,000		35,241,000
Machinery and equipment, including equipment under finance leases
Property, Plant and Equipment
Gross property, plant, and equipment	122,983,000		122,599,000
Construction in progress
Property, Plant and Equipment
Gross property, plant, and equipment	$ 7,692,000		$ 5,234,000

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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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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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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Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services 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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The charge against earnings resulting from the aggregate write down of tangible assets from their carrying value to their fair value.

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