Note 3 - Available-for-sale Securities - Carrying Amount of Securities and Fair Value (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Available-for-sale securities, gross amortized cost	$ 24,707,857	$ 31,951,014
Available-for-sale securities, gross unrealized gains	15,385	53,689
Available-for-sale securities, gross unrealized losses	(323,361)	(505,571)
Available-for-sale securities, fair value	24,399,881	31,499,132
Collateralized Mortgage Backed Securities [Member]
Available-for-sale securities, gross amortized cost	21,028,794	27,524,834
Available-for-sale securities, gross unrealized gains	12,757	45,866
Available-for-sale securities, gross unrealized losses	(272,959)	(442,303)
Available-for-sale securities, fair value	20,768,592	27,128,397
US Government Agencies Debt Securities [Member]
Available-for-sale securities, gross amortized cost	2,006,786	2,588,843
Available-for-sale securities, gross unrealized gains	44	0
Available-for-sale securities, gross unrealized losses	(49,047)	(63,107)
Available-for-sale securities, fair value	1,957,783	2,525,736
US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities, gross amortized cost	1,672,277	1,837,337
Available-for-sale securities, gross unrealized gains	2,584	7,823
Available-for-sale securities, gross unrealized losses	(1,355)	(161)
Available-for-sale securities, fair value	$ 1,673,506	$ 1,844,999

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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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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-Publisher FASB
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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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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-SubTopic 10
-Section S99
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