Note 4 - Loans and the Allowance for Loan Losses - Aging Analysis of the Loan Portfolio (Details) - USD ($)	Jun. 30, 2017	Dec. 31, 2016
Loans, current	$ 469,020,000	$ 456,396,000
Loans	476,091,000	461,123,000
Loans, past due	7,071,000	4,727,000
Financing Receivable, Recorded Investment, Nonaccrual Status	2,910,000	2,724,000
Financing Receivables 30 to 89 Days Past Due [Member]
Loans, past due	4,161,000	2,003,000
Commercial Portfolio Segment [Member] \| Commercial Loans [Member]
Loans, current	38,686,000	41,216,000
Loans	39,394,000	41,293,000
Loans, past due	708,000	77,000
Financing Receivable, Recorded Investment, Nonaccrual Status	90,000
Commercial Portfolio Segment [Member] \| Commercial Loans [Member] \| Financing Receivables 30 to 89 Days Past Due [Member]
Loans, past due	618,000	77,000
Commercial Portfolio Segment [Member] \| Agricultural Loans [Member]
Loans, current	54,672,000	51,103,000
Loans	54,974,000	51,103,000
Loans, past due	302,000
Financing Receivable, Recorded Investment, Nonaccrual Status
Commercial Portfolio Segment [Member] \| Agricultural Loans [Member] \| Financing Receivables 30 to 89 Days Past Due [Member]
Loans, past due	302,000
Commercial Portfolio Segment [Member] \| Real Estate Loan [Member]
Loans, current	233,779,000	224,138,000
Loans	236,791,000	226,136,000
Loans, past due	3,012,000	1,998,000
Financing Receivable, Recorded Investment, Nonaccrual Status	1,422,000	1,479,000
Commercial Portfolio Segment [Member] \| Real Estate Loan [Member] \| Financing Receivables 30 to 89 Days Past Due [Member]
Loans, past due	1,590,000	519,000
Commercial Portfolio Segment [Member] \| Construction Loans [Member]
Loans, current	24,123,000	21,191,000
Loans	24,819,000	21,904,000
Loans, past due	696,000	713,000
Financing Receivable, Recorded Investment, Nonaccrual Status	696,000	703,000
Commercial Portfolio Segment [Member] \| Construction Loans [Member] \| Financing Receivables 30 to 89 Days Past Due [Member]
Loans, past due		10,000
Residential Portfolio Segment [Member] \| Real Estate Loan [Member]
Loans, current	18,668,000	20,959,000
Loans	18,952,000	21,283,000
Loans, past due	284,000	324,000
Financing Receivable, Recorded Investment, Nonaccrual Status	131,000	145,000
Residential Portfolio Segment [Member] \| Real Estate Loan [Member] \| Financing Receivables 30 to 89 Days Past Due [Member]
Loans, past due	153,000	179,000
Residential Portfolio Segment [Member] \| Equity Lines of Credit [Member]
Loans, current	41,356,000	41,736,000
Loans	42,211,000	42,338,000
Loans, past due	855,000	602,000
Financing Receivable, Recorded Investment, Nonaccrual Status	260,000	326,000
Residential Portfolio Segment [Member] \| Equity Lines of Credit [Member] \| Financing Receivables 30 to 89 Days Past Due [Member]
Loans, past due	595,000	276,000
Consumer Portfolio Segment [Member] \| Automobile Loan [Member]
Loans, current	54,075,000	52,565,000
Loans	55,255,000	53,553,000
Loans, past due	1,180,000	988,000
Financing Receivable, Recorded Investment, Nonaccrual Status	308,000	69,000
Consumer Portfolio Segment [Member] \| Automobile Loan [Member] \| Financing Receivables 30 to 89 Days Past Due [Member]
Loans, past due	872,000	919,000
Consumer Portfolio Segment [Member] \| Other Loans [Member]
Loans, current	3,661,000	3,488,000
Loans	3,695,000	3,513,000
Loans, past due	34,000	25,000
Financing Receivable, Recorded Investment, Nonaccrual Status	3,000	2,000
Consumer Portfolio Segment [Member] \| Other Loans [Member] \| Financing Receivables 30 to 89 Days Past Due [Member]
Loans, past due	$ 31,000	$ 23,000

Financing receivables that are current.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7A
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953401-111524

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5111-111524

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82891408&loc=d3e4428-111522

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