Note 5 - Property, Plant and Equipment - Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Mar. 31, 2021
Property, Plant and Equipment, Gross	$ 688,596	$ 644,889
Less: accumulated depreciation	(420,553)	(396,306)
Property, plant and equipment, net	268,043	248,583
Land and Land Improvements [Member]
Property, Plant and Equipment, Gross	42,981	42,647
Building and Building Improvements [Member]
Property, Plant and Equipment, Gross	202,444	188,333
Machinery and Equipment [Member]
Property, Plant and Equipment, Gross	403,192	371,925
Office Furniture, Vehicles and Computer Software [Member]
Property, Plant and Equipment, Gross	10,003	9,404
Construction in Progress [Member]
Property, Plant and Equipment, Gross	$ 29,976	$ 32,580

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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