Property, Plant and Equipment (Details) - USD ($)	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Property, Plant and Equipment
Property, plant and equipment - gross	$ 190,510,000		$ 188,655,000
Less accumulated depreciation and amortization, including accumulated amortization of finance leases	(104,640,000)		(101,798,000)
Property, plant, and equipment - net	85,870,000		86,857,000
Depreciation	2,772,000	$ 2,944,000
Asset impairment	0	$ 0
Land
Property, Plant and Equipment
Property, plant and equipment - gross	12,451,000		12,440,000
Improvements to land and leaseholds
Property, Plant and Equipment
Property, plant and equipment - gross	17,580,000		17,610,000
Buildings
Property, Plant and Equipment
Property, plant and equipment - gross	36,387,000		34,608,000
Machinery and equipment, including equipment under finance leases
Property, Plant and Equipment
Property, plant and equipment - gross	121,658,000		120,914,000
Construction in progress
Property, Plant and Equipment
Property, plant and equipment - gross	$ 2,434,000		$ 3,083,000

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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