Note 4 - Loans and the Allowance for Loan Losses - Aging Analysis of the Loan Portfolio (Details) - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Loans, past due	$ 3,469,000	$ 3,688,000
Loans, 90 days past due and still accruing
Financing Receivable, Nonaccrual	1,457,000	1,117,000
Loans, current	569,977,000	562,511,000
Loans	573,446,000	566,199,000
Loans, 90 days past due and still accruing
Financing Receivables 30 to 89 Days Past Due [Member]
Loans, past due	2,012,000	2,571,000
Commercial Portfolio Segment [Member] \| Commercial Loans [Member]
Loans, past due	315,000	155,000
Loans, 90 days past due and still accruing
Financing Receivable, Nonaccrual	123,000	144,000
Loans, current	42,392,000	49,408,000
Loans	42,707,000	49,563,000
Loans, 90 days past due and still accruing
Commercial Portfolio Segment [Member] \| Commercial Loans [Member] \| Financing Receivables 30 to 89 Days Past Due [Member]
Loans, past due	192,000	11,000
Commercial Portfolio Segment [Member] \| Agricultural Loans [Member]
Loans, past due	69,000
Loans, 90 days past due and still accruing
Financing Receivable, Nonaccrual
Loans, current	69,972,000	69,160,000
Loans	70,041,000	69,160,000
Loans, 90 days past due and still accruing
Commercial Portfolio Segment [Member] \| Agricultural Loans [Member] \| Financing Receivables 30 to 89 Days Past Due [Member]
Loans, past due	69,000
Commercial Portfolio Segment [Member] \| Real Estate Loan [Member]
Loans, past due	764,000	131,000
Loans, 90 days past due and still accruing
Financing Receivable, Nonaccrual	610,000	131,000
Loans, current	281,769,000	271,579,000
Loans	282,533,000	271,710,000
Loans, 90 days past due and still accruing
Commercial Portfolio Segment [Member] \| Real Estate Loan [Member] \| Financing Receivables 30 to 89 Days Past Due [Member]
Loans, past due	154,000
Commercial Portfolio Segment [Member] \| Construction Loans [Member]
Loans, past due	90,000	92,000
Loans, 90 days past due and still accruing
Financing Receivable, Nonaccrual	90,000	92,000
Loans, current	37,547,000	40,069,000
Loans	37,637,000	40,161,000
Loans, 90 days past due and still accruing
Commercial Portfolio Segment [Member] \| Construction Loans [Member] \| Financing Receivables 30 to 89 Days Past Due [Member]
Loans, past due
Residential Portfolio Segment [Member] \| Real Estate Loan [Member]
Loans, past due	156,000	309,000
Loans, 90 days past due and still accruing
Financing Receivable, Nonaccrual	149,000	155,000
Loans, current	16,257,000	15,591,000
Loans	16,413,000	15,900,000
Loans, 90 days past due and still accruing
Residential Portfolio Segment [Member] \| Real Estate Loan [Member] \| Financing Receivables 30 to 89 Days Past Due [Member]
Loans, past due	7,000	154,000
Residential Portfolio Segment [Member] \| Equity Lines of Credit [Member]
Loans, past due	562,000	782,000
Loans, 90 days past due and still accruing
Financing Receivable, Nonaccrual	178,000	186,000
Loans, current	36,957,000	37,708,000
Loans	37,519,000	38,490,000
Loans, 90 days past due and still accruing
Residential Portfolio Segment [Member] \| Equity Lines of Credit [Member] \| Financing Receivables 30 to 89 Days Past Due [Member]
Loans, past due	384,000	596,000
Consumer Portfolio Segment [Member] \| Automobile Loan [Member]
Loans, past due	1,471,000	2,126,000
Loans, 90 days past due and still accruing
Financing Receivable, Nonaccrual	307,000	401,000
Loans, current	81,266,000	75,009,000
Loans	82,737,000	77,135,000
Loans, 90 days past due and still accruing
Consumer Portfolio Segment [Member] \| Automobile Loan [Member] \| Financing Receivables 30 to 89 Days Past Due [Member]
Loans, past due	1,164,000	1,725,000
Consumer Portfolio Segment [Member] \| Other Loans [Member]
Loans, past due	42,000	93,000
Loans, 90 days past due and still accruing
Financing Receivable, Nonaccrual		8,000
Loans, current	3,817,000	3,987,000
Loans	3,859,000	4,080,000
Loans, 90 days past due and still accruing
Consumer Portfolio Segment [Member] \| Other Loans [Member] \| Financing Receivables 30 to 89 Days Past Due [Member]
Loans, past due	$ 42,000	$ 85,000

Amount of financing receivable 90 days or more past due and still accruing.

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