Note 4 - Investment Securities Available for Sale - Amortized Cost and Fair Value of Securities (Details) - USD ($)	Jun. 30, 2018	Mar. 31, 2018
Securities available for sale, amortized cost	$ 75,761,501	$ 78,267,079
Securities available for sale, gross unrealized gains	4,212	12,993
Securities available for sale, gross unrealized losses	3,127,016	2,875,936
Investment securities available for sale, at fair value	72,638,697	75,404,136
US Government Agencies Debt Securities [Member]
Securities available for sale, amortized cost	2,750,087	2,753,346
Securities available for sale, gross unrealized gains
Securities available for sale, gross unrealized losses	34,435	34,697
Investment securities available for sale, at fair value	2,715,652	2,718,649
US States and Political Subdivisions Debt Securities [Member]
Securities available for sale, amortized cost	12,405,766	12,435,068
Securities available for sale, gross unrealized gains
Securities available for sale, gross unrealized losses	772,923	729,077
Investment securities available for sale, at fair value	11,632,843	11,705,991
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	16,750	45,924
Investment securities available for sale, at fair value	1,983,250	1,954,076
Collateralized Mortgage Backed Securities [Member]
Securities available for sale, amortized cost	58,605,648	61,078,665
Securities available for sale, gross unrealized gains	4,212	12,993
Securities available for sale, gross unrealized losses	2,302,908	2,066,238
Investment securities available for sale, at fair value	$ 56,306,952	$ 59,025,420

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on 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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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
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