Note 16 - Fair Values of Financial Instruments - Estimated Fair Values of Financial Instruments (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Reported Value Measurement [Member]
Cash and cash equivalents	$ 3,755,817	$ 5,946,649
Time deposits	250,000	250,000
Federal funds sold	939,000	1,690,000
Securities	26,964,062	45,314,001
Accrued interest receivable	794,449	785,484
Net loans	207,035,091	160,586,129
Loans held for sale	499,375	305,072
Mortgage servicing rights	423,522	351,544
Accrued interest payable	661	224
FHLB advances	15,105,287	1,121,153
Reported Value Measurement [Member] \| Non-Interest Bearing Deposits [Member]
Deposits	11,562,801	9,974,536
Reported Value Measurement [Member] \| Interest Bearing Deposits, Liabilities [Member]
Deposits	171,211,823	162,572,485
Estimate of Fair Value Measurement [Member]
Cash and cash equivalents	3,755,817	5,946,649
Time deposits	250,000	250,000
Federal funds sold	939,000	1,690,000
Securities	26,964,062	45,314,001
Accrued interest receivable	794,449	785,484
Net loans	208,823,729	161,967,000
Loans held for sale	499,375	305,072
Mortgage servicing rights	423,522	351,544
Accrued interest payable	661	224
FHLB advances	15,080,025	1,151,000
Estimate of Fair Value Measurement [Member] \| Non-Interest Bearing Deposits [Member]
Deposits	11,562,801	9,974,536
Estimate of Fair Value Measurement [Member] \| Interest Bearing Deposits, Liabilities [Member]
Deposits	171,915,595	155,963,464
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents	3,755,817	5,946,649
Time deposits	250,000	250,000
Federal funds sold	939,000	1,690,000
Securities
Accrued interest receivable	794,449	785,484
Net loans
Loans held for sale
Mortgage servicing rights
Accrued interest payable	661	224
FHLB advances
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 1 [Member] \| Non-Interest Bearing Deposits [Member]
Deposits	11,562,801	9,974,536
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 1 [Member] \| Interest Bearing Deposits, Liabilities [Member]
Deposits
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 2 [Member]
Cash and cash equivalents
Time deposits
Federal funds sold
Securities	26,045,675	44,560,680
Accrued interest receivable
Net loans
Loans held for sale	499,375	305,072
Mortgage servicing rights
Accrued interest payable
FHLB advances	15,080,025	1,151,000
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 2 [Member] \| Non-Interest Bearing Deposits [Member]
Deposits
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 2 [Member] \| Interest Bearing Deposits, Liabilities [Member]
Deposits
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 3 [Member]
Cash and cash equivalents
Time deposits
Federal funds sold
Securities	918,387	753,321
Accrued interest receivable
Net loans	208,823,729	161,967,000
Loans held for sale
Mortgage servicing rights	423,522	351,544
Accrued interest payable
FHLB advances
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 3 [Member] \| Non-Interest Bearing Deposits [Member]
Deposits
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 3 [Member] \| Interest Bearing Deposits, Liabilities [Member]
Deposits	$ 171,915,595	$ 155,963,464

Fair value portion of interest payable.

No definition available.

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- Definition

Fair value portion of interest receivable.

+ References

No definition available.

+ Details

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- Definition

Fair value portion of time deposit assets held by the entity.

+ References

No definition available.

+ Details

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- Definition

Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

+ References

No definition available.

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- Definition

Fair value portion of deposit liabilities held by the entity, including, but not limited to, foreign and domestic, interest and noninterest bearing, demand deposits, saving deposits, negotiable orders of withdrawal (NOW) and time deposits.

+ References

No definition available.

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- Definition

Fair value portion of federal funds sold and securities borrowed or purchased under agreements to resell.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.13(3)(a))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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- Definition

Fair value portion of borrowing from Federal Home Loan Bank (FHLBank).

+ References

+ Details

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- Definition

Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(12))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(5))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 35
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82895926&loc=d3e24584-111560

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(6))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(2))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=75030427&loc=d3e22054-111558

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(1))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value portion of loans held-for-sale including, but not limited to, mortgage loans and finance receivables.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
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Balance Type:	debit
Period Type:	instant

- Definition

Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-URI http://asc.fasb.org/subtopic&trid=2196772

+ Details

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Balance Type:	debit
Period Type:	instant

- Definition

Fair value of an asset representing net future revenue from contractually specified servicing fees, late charges, and other ancillary revenues, in excess of future costs related to servicing arrangements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=68078379&loc=d3e122625-111746

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