Note 4 - Equipment and Leasehold Improvements - Components of Equipment and Leasehold Improvements (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Mar. 31, 2024
Equipment and leasehold improvements, gross	$ 37,436	$ 37,398
Less accumulated depreciation and amortization	(28,578)	(27,500)
Construction-in-progress	398	211
Equipment and leasehold improvements, net	9,256	10,109
Equipment [Member]
Equipment and leasehold improvements, gross	21,942	21,904
Leasehold Improvements [Member]
Equipment and leasehold improvements, gross	15,075	15,075
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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