Note 4 - Property - Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Property, plant and equipment, gross	$ 51,988	$ 51,956
Less accumulated depreciation	33,745	33,445
Property, net	18,243	18,511
Land [Member]
Property, plant and equipment, gross	5,072	5,072
Land Improvements [Member]
Property, plant and equipment, gross	12,943	12,943
Building [Member]
Property, plant and equipment, gross	23,465	23,465
Machinery and Equipment [Member]
Property, plant and equipment, gross	10,485	10,476
Construction in Progress [Member]
Property, plant and equipment, gross	$ 23

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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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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