Note 3 - Stock-based Compensation (Details Textual) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Sep. 30, 2020	Sep. 30, 2020	Sep. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross (in shares)	0	0	5,939
Restricted Stock [Member]
Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture, Total (in shares)		688,167	170,500
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total	$ 5.9	$ 5.9
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)		2 years 73 days
Restricted Stock [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)		2 years
Restricted Stock [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)		3 years
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, Total	$ 0.1	$ 0.1
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)		219 days
Common Stock [Member]
Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture, Total (in shares)		27,341	13,174

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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