Note 10 - Property, Plant and Equipment - Cost and Accumulated Depreciation of Property and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Mar. 31, 2021
Property, plant and equipment, gross	$ 58,315	$ 51,413
Less accumulated depreciation	(43,704)	(42,416)
Property, plant and equipment, net	14,611	8,997
Construction in Progress [Member]
Property, plant and equipment, gross	432	220
Land [Member]
Property, plant and equipment, gross	980	270
Building [Member]
Property, plant and equipment, gross	5,270	1,630
Equipment and Software [Member]
Property, plant and equipment, gross	43,714	41,652
Finance Lease, Right-of-use [Member]
Property, plant and equipment, gross	11	0
Furniture and Fixtures [Member]
Property, plant and equipment, gross	1,385	1,333
Leasehold Improvements [Member]
Property, plant and equipment, gross	$ 6,523	$ 6,308