Note 2 - Summary of Significant Accounting Policies - Weighted Average Number of Shares (Details) - shares	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Basic (in shares)	4,834,054	4,845,627
Dilutive effect of stock options (in shares)	408	1,667
Shares used in computing net income per share – diluted (in shares)	4,834,462	4,847,294