Note 8 - Income Taxes (Details Textual) - USD ($)	3 Months Ended			6 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Tax Expense (Benefit), Total	$ 1,982,000	$ 2,463,000		$ 3,342,000	$ 4,476,000
Effective Income Tax Rate Reconciliation, Percent, Total	23.80%	22.60%		23.70%	21.70%
Proceeds from Income Tax Refunds			$ 285,000