Note 4 - Equipment and Leasehold Improvements - Components of Equipment and Leasehold Improvements (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Mar. 31, 2022
Equipment and leasehold improvements, gross	$ 35,680	$ 35,376
Less accumulated depreciation and amortization	(25,164)	(24,339)
Construction-in-progress	1,231	848
Equipment and leasehold improvements, net	11,747	11,885
Equipment [Member]
Equipment and leasehold improvements, gross	20,493	20,231
Leasehold Improvements [Member]
Equipment and leasehold improvements, gross	14,786	14,751
Furniture and Fixtures [Member]
Equipment and leasehold improvements, gross	$ 401	$ 394

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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