Note 4 - Equipment and Leasehold Improvements - Components of Equipment and Leasehold Improvements (Details) - USD ($) $ in Thousands	Jun. 30, 2025	Mar. 31, 2025
Equipment and leasehold improvements, gross	$ 37,524	$ 37,529
Less accumulated depreciation and amortization	(29,235)	(28,885)
Construction-in-progress	301	283
Equipment and leasehold improvements, net	8,590	8,927
Equipment [Member]
Equipment and leasehold improvements, gross	21,967	21,972
Leasehold Improvements [Member]
Equipment and leasehold improvements, gross	15,138	15,138
Furniture and Fixtures [Member]
Equipment and leasehold improvements, gross	$ 419	$ 419

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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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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