Note 4 - Components of Common Shares Outstanding (Details) - shares	3 Months Ended		6 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Basic (in shares)	4,855,398	4,855,071	4,858,557	4,853,068
Dilutive effect of stock options (in shares)	2,735	16,958	3,874	15,701
Shares used in computing net income per share – diluted (in shares)	4,858,133	4,872,029	4,862,431	4,868,769