Note 4 - Earnings Per Share - Basic and Diluted Earnings Per Share (Details) - USD ($)	3 Months Ended		6 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Net income (loss)	$ 323,486	$ (201,085)	$ (11,723)	$ (82,678)
Average common shares outstanding - basic (in shares)	3,176,654	3,166,309	3,176,654	3,166,110
Average common shares outstanding - diluted (in shares)	3,176,654	3,166,780	3,176,654	3,166,581
Income (loss) per common share - basic and diluted (in dollars per share)	$ 0.10	$ (0.06)	$ 0	$ (0.03)