Note 12 - Fair Value Measurement and Disclosure - Estimated Fair Values of Financial Instruments (Details) - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Reported Value Measurement [Member]
Financial Assets:
Cash and cash equivalents	$ 7,302,629	$ 8,430,458
Time deposits	250,000	250,000
Federal funds sold	4,409,000	5,663,000
Securities	24,469,999	25,533,767
Net loans	235,793,257	235,926,419
Loans held for sale	250,505
Accrued interest receivable	841,005	824,542
Mortgage servicing rights	437,061	446,375
Financial Liabilities:
Accrued interest payable	16,146	5,648
FHLB advances	10,588,245	12,087,152
Reported Value Measurement [Member] \| Non-Interest Bearing Deposits [Member]
Financial Liabilities:
Deposits	13,747,615	14,057,719
Reported Value Measurement [Member] \| Interest Bearing Deposits, Liabilities [Member]
Financial Liabilities:
Deposits	207,494,542	209,390,810
Estimate of Fair Value Measurement [Member]
Financial Assets:
Cash and cash equivalents	7,302,629	8,430,458
Time deposits	250,000	250,000
Federal funds sold	4,409,000	5,663,000
Securities	24,469,999	25,533,767
Net loans	233,769,242	232,996,807
Loans held for sale	250,505
Accrued interest receivable	841,005	824,542
Mortgage servicing rights	437,061	446,375
Financial Liabilities:
Accrued interest payable	16,146	5,648
FHLB advances	10,692,350	12,136,386
Estimate of Fair Value Measurement [Member] \| Non-Interest Bearing Deposits [Member]
Financial Liabilities:
Deposits	13,747,615	14,057,719
Estimate of Fair Value Measurement [Member] \| Interest Bearing Deposits, Liabilities [Member]
Financial Liabilities:
Deposits	207,890,710	209,576,569
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 1 [Member]
Financial Assets:
Cash and cash equivalents	7,302,629	8,430,458
Time deposits	250,000	250,000
Federal funds sold	4,409,000	5,663,000
Securities
Net loans
Loans held for sale
Accrued interest receivable	841,005	824,542
Mortgage servicing rights
Financial Liabilities:
Accrued interest payable	16,146	5,648
FHLB advances
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 1 [Member] \| Non-Interest Bearing Deposits [Member]
Financial Liabilities:
Deposits	13,747,615	14,057,719
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 1 [Member] \| Interest Bearing Deposits, Liabilities [Member]
Financial Liabilities:
Deposits
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 2 [Member]
Financial Assets:
Cash and cash equivalents
Time deposits
Federal funds sold
Securities	24,469,999	25,533,767
Net loans
Loans held for sale	250,505
Accrued interest receivable
Mortgage servicing rights
Financial Liabilities:
Accrued interest payable
FHLB advances	10,692,350	12,136,836
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 2 [Member] \| Non-Interest Bearing Deposits [Member]
Financial Liabilities:
Deposits
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 2 [Member] \| Interest Bearing Deposits, Liabilities [Member]
Financial Liabilities:
Deposits
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 3 [Member]
Financial Assets:
Cash and cash equivalents
Time deposits
Federal funds sold
Securities
Net loans	233,769,242	232,996,807
Loans held for sale
Accrued interest receivable
Mortgage servicing rights	437,061	446,375
Financial Liabilities:
Accrued interest payable
FHLB advances
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 3 [Member] \| Non-Interest Bearing Deposits [Member]
Financial Liabilities:
Deposits
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 3 [Member] \| Interest Bearing Deposits, Liabilities [Member]
Financial Liabilities:
Deposits	$ 207,890,710	$ 209,576,569

Fair value portion of interest payable.

No definition available.

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- Definition

Fair value portion of interest receivable.

+ References

No definition available.

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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.

+ Details

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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://fasb.org/us-gaap/role/ref/legacyRef
-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

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- References

No definition available.

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- References

No definition available.

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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/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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- 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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- 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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-URI http://asc.fasb.org/subtopic&trid=2196772

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Namespace Prefix:	us-gaap_
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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/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6469459&loc=d3e122501-111745

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=116651436&loc=d3e122625-111746

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