Property, Plant and Equipment (Details) - USD ($)	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Property, Plant and Equipment
Gross property, plant, and equipment	$ 170,251,000		$ 168,638,000
Less accumulated depreciation and amortization, including accumulated amortization of finance leases	(108,668,000)		(106,553,000)
Property, plant, and equipment - net	61,583,000		62,085,000
Depreciation	1,990,000	$ 1,935,000
Impairments of property, plant, and equipment	0	$ 0
Land
Property, Plant and Equipment
Gross property, plant, and equipment	6,632,000		6,627,000
Improvements to land and leaseholds
Property, Plant and Equipment
Gross property, plant, and equipment	17,573,000		17,573,000
Buildings
Property, Plant and Equipment
Gross property, plant, and equipment	27,487,000		27,348,000
Machinery and equipment, including equipment under finance leases
Property, Plant and Equipment
Gross property, plant, and equipment	117,272,000		116,175,000
Construction in progress
Property, Plant and Equipment
Gross property, plant, and equipment	$ 1,287,000		$ 915,000

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 amount of write-downs for impairments recognized during the period for long-lived assets held for abandonment, exchange or sale.

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Amount of accumulated depreciation and amortization from plant, property, and equipment and right-of-use asset from finance lease.

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Amount, after accumulated depreciation and amortization, of property, plant, and equipment and finance lease right-of-use asset.

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Amount, before accumulated depreciation and amortization, of property, plant, and equipment and finance lease right-of-use asset.

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