Note 4 - Equipment and Leasehold Improvements - Components of Equipment and Leasehold Improvements (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Mar. 31, 2021
Equipment and leasehold improvements, gross	$ 35,255	$ 34,131
Less accumulated depreciation and amortization	(23,942)	(22,740)
Construction-in-progress	623	745
Equipment and leasehold improvements, net	11,936	12,136
Equipment [Member]
Equipment and leasehold improvements, gross	20,128	19,056
Leasehold Improvements [Member]
Equipment and leasehold improvements, gross	14,751	14,703
Furniture and Fixtures [Member]
Equipment and leasehold improvements, gross	$ 376	$ 372

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 of structure or a modification to a structure under construction. Includes recently completed structures or modifications to structures that have not been placed into service.

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