Note 6 - Investment Securities Available for Sale - Debt Securities By Contractual Maturity (Details) - USD ($)	Mar. 31, 2018	Mar. 31, 2017
Amortized cost, securities available for sale, maturing within one year	$ 2,009,160
Fair value, securities available for sale, maturing within one year	1,995,625
Amortized cost, securities available for sale, maturing over one to five years	1,231,928	4,234,642
Fair value, securities available for sale, maturing over one to five years	1,196,368	4,240,740
Amortized cost, securities available for sale maturing over five to ten years	3,578,827	5,538,313
Fair value, securities available for sale, maturing over five to ten years	3,500,641	5,404,810
Amortized cost, securities available for sale, maturing over ten years	10,368,499	12,848,895
Fair value, securities available for sale, maturing over ten years	9,686,082	11,951,114
Amortized cost of mortgage-backed securities, in monthly installments	61,078,665	81,994,305
Fair value of mortgage-backed securities, in monthly installments	59,025,420	80,832,464
Amortized cost of securities available for sale	78,267,079	104,616,155
Fair value of securities available for sale	$ 75,404,136	$ 102,429,128

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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