Note 4 - Securities - Available-for-sale Debt Securities (Details) - USD ($)	Jun. 30, 2018	Dec. 31, 2017
Available-for-sale securities, amortized cost	$ 91,713,756	$ 82,323,052
Available-for-sale securities, gross unrealized gains	58,405	328,155
Available-for-sale securities, gross unrealized (losses)	(2,455,168)	(1,172,534)
Available-for-sale securities	89,316,993	81,478,673
US Government Corporations and Agencies Securities [Member]
Available-for-sale securities, amortized cost	5,537,396
Available-for-sale securities, gross unrealized gains	10,914
Available-for-sale securities, gross unrealized (losses)	(176)
Available-for-sale securities	5,548,134
US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities, amortized cost	32,746,933	33,908,207
Available-for-sale securities, gross unrealized gains	6,975	253,872
Available-for-sale securities, gross unrealized (losses)	(883,396)	(263,621)
Available-for-sale securities	31,870,512	33,898,458
Corporate Debt Securities [Member]
Available-for-sale securities, amortized cost	3,000,000	3,000,000
Available-for-sale securities, gross unrealized gains	22,500	65,000
Available-for-sale securities, gross unrealized (losses)	(166)
Available-for-sale securities	3,022,334	3,065,000
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Available-for-sale securities, amortized cost	50,429,427	45,414,845
Available-for-sale securities, gross unrealized gains	18,016	9,283
Available-for-sale securities, gross unrealized (losses)	(1,571,430)	(908,913)
Available-for-sale securities	$ 48,876,013	$ 44,515,215

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).

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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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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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Amount 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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