Note 2 - Summary of Significant Accounting Policies - Weighted Average Number of Shares (Details) - shares	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Weighted average common shares outstanding – basic (in shares)	4,845,627	4,844,010
Dilutive effect of stock options (in shares)	1,667	6,557
Shares used in computing net income per share – diluted (in shares)	4,847,294	4,850,567