Note 5 - Investment Securities Available for Sale - Securities In a Continuous Unrealized Loss Position (Details) - USD ($)	Sep. 30, 2017	Mar. 31, 2017
Less than 12 months, gross unrealized losses	$ 271,646	$ 1,905,072
Less than 12 months, fair value	25,609,713	84,192,747
12 months or longer, gross unrealized losses	1,375,725	369,230
12 months or longer, fair value	52,590,893	8,933,268
Total gross unrealized losses	1,647,371	2,274,302
Total fair value	78,200,606	93,126,015
US Government Agencies Debt Securities [Member]
Less than 12 months, gross unrealized losses	15,427	13,393
Less than 12 months, fair value	2,744,435	3,256,964
12 months or longer, gross unrealized losses
12 months or longer, fair value
Total gross unrealized losses	15,427	13,393
Total fair value	2,744,435	3,256,964
Municipal Bonds [Member]
Less than 12 months, gross unrealized losses		950,496
Less than 12 months, fair value		13,982,251
12 months or longer, gross unrealized losses	532,682
12 months or longer, fair value	11,960,989
Total gross unrealized losses	532,682	950,496
Total fair value	11,960,989	13,982,251
Corporate Bond Securities [Member]
Less than 12 months, gross unrealized losses
Less than 12 months, fair value
12 months or longer, gross unrealized losses	80,564	83,478
12 months or longer, fair value	1,919,436	1,916,522
Total gross unrealized losses	80,564	83,478
Total fair value	1,919,436	1,916,522
Collateralized Mortgage Backed Securities [Member]
Less than 12 months, gross unrealized losses	256,219	941,183
Less than 12 months, fair value	22,865,278	66,953,532
12 months or longer, gross unrealized losses	762,479	285,752
12 months or longer, fair value	38,710,468	7,016,746
Total gross unrealized losses	1,018,698	1,226,935
Total fair value	$ 61,575,746	$ 73,970,278