Note 2 - Summary of Significant Accounting Policies - Weighted Average Number of Shares (Details) - shares	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Basic (in shares)	4,836,602	4,850,209	4,855,504
Dilutive effect of stock options (in shares)	1,787	2,393	16,431
Shares used in computing net income per share – diluted (in shares)	4,838,389	4,852,602	4,871,935