Note 3 - Stock-based Compensation (Details Textual) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Restricted Stock [Member]
Shares Issued, Shares, Share-Based Payment Arrangement, after Forfeiture (in shares)	9,000	338,500	681,500	338,500
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount	$ 6.8		$ 6.8
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)			2 years
Restricted Stock [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)			2 years
Immediately Vested Common Stock [Member]
Shares Issued, Shares, Share-Based Payment Arrangement, after Forfeiture (in shares)	0	0	53,675	25,806
Share-Based Payment Arrangement, Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)				2 years
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount	$ 0.1		$ 0.1
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)			8 months 12 days
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross (in shares)	0	0	0	20,564

Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Number, after forfeiture, of shares or units issued under share-based payment arrangement. Excludes shares or units issued under employee stock ownership plan (ESOP).

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