Note 4 - Allowance for Loan Losses - Segregated by Impairment Methodology (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Ending allowance balance, individually evaluated for impairment	$ 1,474		$ 1,567
Ending allowance balance, collectively evaluated for impairment	5,685		6,476
Ending allowance balance	7,159	$ 7,508	8,043	$ 8,923
Ending loan balance, individually evaluated for impairment	18,692		20,778
Ending loan balance, collectively evaluated for impairment	748,104		754,788
Ending loan balance	766,796	765,284	775,566
Loans	766,796	765,284	775,566
Commercial [Member] \| Commercial and Agricultural Portfolio Segment [Member]
Ending allowance balance, individually evaluated for impairment	0		0
Ending allowance balance, collectively evaluated for impairment	444		425
Ending allowance balance	444	447	425	456
Ending loan balance, individually evaluated for impairment	77		33
Ending loan balance, collectively evaluated for impairment	44,952		44,850
Ending loan balance	45,029	48,122	44,883
Loans	45,029	48,122	44,883
Commercial [Member] \| Real Estate Portfolio Segment [Member]
Ending allowance balance, individually evaluated for impairment	1,371		1,517
Ending allowance balance, collectively evaluated for impairment	3,035		3,146
Ending allowance balance	4,406	3,874	4,663	5,751
Ending loan balance, individually evaluated for impairment	15,187		17,292
Ending loan balance, collectively evaluated for impairment	336,876		338,509
Ending loan balance	352,063	351,172	355,801
Loans	352,063	351,172	355,801
Agricultural [Member] \| Commercial and Agricultural Portfolio Segment [Member]
Ending allowance balance, individually evaluated for impairment	0		0
Ending allowance balance, collectively evaluated for impairment	262		238
Ending allowance balance	262	186	238	168
Ending loan balance, individually evaluated for impairment	5		5
Ending loan balance, collectively evaluated for impairment	20,032		21,805
Ending loan balance	20,037	16,443	21,810
Loans	20,037	16,443	21,810
Commercial Construction [Member] \| Real Estate Portfolio Segment [Member]
Ending allowance balance, individually evaluated for impairment	54		4
Ending allowance balance, collectively evaluated for impairment	28		766
Ending allowance balance	82	1,216	770	323
Ending loan balance, individually evaluated for impairment	481		72
Ending loan balance, collectively evaluated for impairment	48,428		35,079
Ending loan balance	48,909	45,214	35,151
Loans	48,909	45,214	35,151
Residential Construction [Member] \| Real Estate Portfolio Segment [Member]
Ending allowance balance, individually evaluated for impairment	0		0
Ending allowance balance, collectively evaluated for impairment	0		11
Ending allowance balance	0		11	13
Ending loan balance, individually evaluated for impairment	0		0
Ending loan balance, collectively evaluated for impairment	11,541		9,230
Ending loan balance	11,541	8,583	9,230
Loans	11,541	8,583	9,230
Residential [Member] \| Real Estate Portfolio Segment [Member]
Ending allowance balance, individually evaluated for impairment	21		20
Ending allowance balance, collectively evaluated for impairment	1,045		952
Ending allowance balance	1,066	968	972	1,396
Ending loan balance, individually evaluated for impairment	1,910		2,336
Ending loan balance, collectively evaluated for impairment	185,681		198,236
Ending loan balance	187,591	194,049	200,572
Loans	187,591	194,049	200,572
Farmland [Member] \| Real Estate Portfolio Segment [Member]
Ending allowance balance, individually evaluated for impairment	28		26
Ending allowance balance, collectively evaluated for impairment	840		833
Ending allowance balance	868	780	859	722
Ending loan balance, individually evaluated for impairment	1,032		1,040
Ending loan balance, collectively evaluated for impairment	66,835		69,154
Ending loan balance	67,867	67,768	70,194
Loans	67,867	67,768	70,194
Consumer [Member] \| Consumer and Other Portfolio Segment [Member]
Ending allowance balance, individually evaluated for impairment	0		0
Ending allowance balance, collectively evaluated for impairment	30		84
Ending allowance balance	30	34	84	80
Ending loan balance, individually evaluated for impairment	0		0
Ending loan balance, collectively evaluated for impairment	18,746		19,134
Ending loan balance	18,746	18,956	19,134
Loans	18,746	18,956	19,134
Other [Member] \| Consumer and Other Portfolio Segment [Member]
Ending allowance balance, individually evaluated for impairment	0		0
Ending allowance balance, collectively evaluated for impairment	1		21
Ending allowance balance	1	3	21	$ 14
Ending loan balance, individually evaluated for impairment	0		0
Ending loan balance, collectively evaluated for impairment	15,013		18,791
Ending loan balance	15,013	14,977	18,791
Loans	$ 15,013	$ 14,977	$ 18,791

The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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