Note 9 - Property, Plant and Equipment - Cost and Accumulated Depreciation of Property and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Mar. 31, 2020
Property, plant and equipment, gross	$ 50,173	$ 48,646
Less accumulated depreciation	(42,033)	(40,081)
Property, plant and equipment, net	8,140	8,565
Construction in Progress [Member]
Property, plant and equipment, gross	718	3,130
Equipment and Software [Member]
Property, plant and equipment, gross	42,015	41,737
Furniture and Fixtures [Member]
Property, plant and equipment, gross	1,326	1,302
Leasehold Improvements [Member]
Property, plant and equipment, gross	$ 6,114	$ 2,477

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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