Note 6 - Investment Securities Available for Sale - Amortized Cost and Fair Value of Securities (Details) - USD ($)	Mar. 31, 2018	Mar. 31, 2017
Securities available for sale, amortized cost	$ 78,267,079	$ 104,616,155
Securities available for sale, gross unrealized gains	12,993	87,275
Securities available for sale, gross unrealized losses	2,875,936	2,274,302
Investment securities available-for-sale	75,404,136	102,429,128
US Government Agencies Debt Securities [Member]
Securities available for sale, amortized cost	2,753,346	3,525,373
Securities available for sale, gross unrealized gains		323
Securities available for sale, gross unrealized losses	34,697	13,393
Investment securities available-for-sale	2,718,649	3,512,303
US States and Political Subdivisions Debt Securities [Member]
Securities available for sale, amortized cost	12,435,068	17,096,477
Securities available for sale, gross unrealized gains		21,858
Securities available for sale, gross unrealized losses	729,077	950,496
Investment securities available-for-sale	11,705,991	16,167,839
Corporate Debt Securities [Member]
Securities available for sale, amortized cost	2,000,000	2,000,000
Securities available for sale, gross unrealized gains
Securities available for sale, gross unrealized losses	45,924	83,478
Investment securities available-for-sale	1,954,076	1,916,522
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Securities available for sale, amortized cost	61,078,665	81,994,305
Securities available for sale, gross unrealized gains	12,993	65,094
Securities available for sale, gross unrealized losses	2,066,238	1,226,935
Investment securities available-for-sale	$ 59,025,420	$ 80,832,464