Note 3 - Investment Securities - Amortized Cost and Fair Value of Investment Securities (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Securities held to maturity:
Securities held to maturity, at amortized cost	$ 379,474,205	$ 322,909,056
Securities held to maturity, gross unrealized gains	2,763,718	2,200,577
Securities held to maturity, gross unrealized (losses)	(2,488,119)	(4,694,734)
Securities held to maturity, fair value	379,749,804	320,414,899
Securities available for sale:
Securities available for sale, amortized cost	274,058,995	253,609,401
Securities available for sale, gross unrealized gains	1,749,323	1,437,658
Securities available for sale, gross unrealized (losses)	(2,900,411)	(3,933,920)
Securities available for sale, fair value	272,907,907	251,113,139
US States and Political Subdivisions Debt Securities [Member]
Securities held to maturity:
Securities held to maturity, at amortized cost	378,424,205	321,859,056
Securities held to maturity, gross unrealized gains	2,763,718	2,200,577
Securities held to maturity, gross unrealized (losses)	(2,488,119)	(4,694,734)
Securities held to maturity, fair value	378,699,804	319,364,899
Securities available for sale:
Securities available for sale, amortized cost	66,176,364	52,816,541
Securities available for sale, gross unrealized gains	660,232	425,801
Securities available for sale, gross unrealized (losses)	(211,100)	(637,916)
Securities available for sale, fair value	66,625,496	52,604,426
Other Securities [Member]
Securities held to maturity:
Securities held to maturity, at amortized cost	1,050,000	1,050,000
Securities held to maturity, gross unrealized gains
Securities held to maturity, gross unrealized (losses)
Securities held to maturity, fair value	1,050,000	1,050,000
Securities available for sale:
Securities available for sale, amortized cost	4,014,004	4,046,332
Securities available for sale, gross unrealized gains	896,384	703,978
Securities available for sale, gross unrealized (losses)	(25,815)	(27,331)
Securities available for sale, fair value	4,884,573	4,722,979
US Government Agencies Debt Securities [Member]
Securities available for sale:
Securities available for sale, amortized cost	38,409,157	46,281,306
Securities available for sale, gross unrealized gains	37,344	132,886
Securities available for sale, gross unrealized (losses)	(349,967)	(330,585)
Securities available for sale, fair value	38,096,534	46,083,607
Residential Mortgage Backed Securities [Member]
Securities available for sale:
Securities available for sale, amortized cost	165,459,470	150,465,222
Securities available for sale, gross unrealized gains	155,363	174,993
Securities available for sale, gross unrealized (losses)	(2,313,529)	(2,938,088)
Securities available for sale, fair value	$ 163,301,304	$ 147,702,127

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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-Publisher FASB
-Name Accounting Standards Codification
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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Amount of accumulated unrealized gain on investments in debt securities classified as held-to-maturity.

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Amount before other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

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Fair value of investments in debt securities classified as held-to-maturity.

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