Note 5 - Allowance for Loan Losses - Segregated by Impairment Methodology (Details) - USD ($)	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Ending Allowance Balance, individually evaluated for impairment	$ 1,639,000		$ 1,487,000
Ending Allowance Balance, collectively evaluated for impairment	4,953,000		5,668,000
Related allowance	1,639,000	$ 1,418,000	1,487,000
Ending Allowance Balance Total	6,600,000	7,277,000	7,155,000	$ 7,508,000
Ending Loan Balance, individually evaluated for impairment	18,047,000		19,557,000
Ending Loan Balance, collectively evaluated for impairment	940,521,000		759,886,000
Impaired balance	21,724,000	24,473,000	23,535,000
Loans	958,723,000	782,027,000	779,443,000
Financial Asset Acquired with Credit Deterioration [Member]
Related allowance	8,000	0	0
Impaired balance	155,000	0	0
Real Estate Portfolio Segment [Member] \| Financial Asset Acquired with Credit Deterioration [Member]
Impaired balance	66,000
Commercial [Member] \| Commercial and Agricultural Portfolio Segment [Member]
Ending Allowance Balance, individually evaluated for impairment	152,000		0
Ending Allowance Balance, collectively evaluated for impairment	291,000		384,000
Related allowance	152,000	6,000	0
Ending Allowance Balance Total	443,000	370,000	384,000	447,000
Ending Loan Balance, individually evaluated for impairment	428,000		39,000
Ending Loan Balance, collectively evaluated for impairment	75,765,000		47,253,000
Impaired balance	901,000	637,000	472,000
Loans	76,232,000	57,410,000	47,292,000
Commercial [Member] \| Commercial and Agricultural Portfolio Segment [Member] \| Financial Asset Acquired with Credit Deterioration [Member]
Related allowance	0
Impaired balance	39,000
Commercial [Member] \| Real Estate Portfolio Segment [Member]
Ending Allowance Balance, individually evaluated for impairment	823,000		1,394,000
Ending Allowance Balance, collectively evaluated for impairment	2,467,000		2,887,000
Related allowance	823,000	1,276,000	1,394,000
Ending Allowance Balance Total	3,290,000	4,549,000	4,281,000	3,874,000
Ending Loan Balance, individually evaluated for impairment	11,967,000		15,164,000
Ending Loan Balance, collectively evaluated for impairment	438,733,000		334,244,000
Impaired balance	12,256,000	15,855,000	15,558,000
Loans	450,700,000	373,534,000	349,408,000
Commercial [Member] \| Real Estate Portfolio Segment [Member] \| Financial Asset Acquired with Credit Deterioration [Member]
Related allowance
Impaired balance
Agricultural [Member] \| Commercial and Agricultural Portfolio Segment [Member]
Ending Allowance Balance, individually evaluated for impairment	586,000		0
Ending Allowance Balance, collectively evaluated for impairment	285,000		315,000
Related allowance	586,000	0	0
Ending Allowance Balance Total	871,000	248,000	315,000	186,000
Ending Loan Balance, individually evaluated for impairment	848,000		27,000
Ending Loan Balance, collectively evaluated for impairment	19,893,000		21,388,000
Impaired balance	1,215,000	413,000	423,000
Loans	20,741,000	16,799,000	21,415,000
Agricultural [Member] \| Commercial and Agricultural Portfolio Segment [Member] \| Financial Asset Acquired with Credit Deterioration [Member]
Related allowance
Impaired balance
Commercial Construction [Member] \| Real Estate Portfolio Segment [Member]
Ending Allowance Balance, individually evaluated for impairment			44,000
Ending Allowance Balance, collectively evaluated for impairment	142,000		81,000
Related allowance	0	39,000	44,000
Ending Allowance Balance Total	142,000	115,000	125,000	1,216,000
Ending Loan Balance, individually evaluated for impairment	67,000		471,000
Ending Loan Balance, collectively evaluated for impairment	73,867,000		53,099,000
Impaired balance	143,000	531,000	573,000
Loans	74,000,000	47,849,000	53,570,000
Commercial Construction [Member] \| Real Estate Portfolio Segment [Member] \| Financial Asset Acquired with Credit Deterioration [Member]
Related allowance	0
Impaired balance	66,000
Residential Construction [Member] \| Real Estate Portfolio Segment [Member]
Ending Allowance Balance, individually evaluated for impairment			0
Ending Allowance Balance, collectively evaluated for impairment	33,000		17,000
Related allowance	0	0	0
Ending Allowance Balance Total	33,000	16,000	17,000
Ending Loan Balance, individually evaluated for impairment			0
Ending Loan Balance, collectively evaluated for impairment	20,039,000		12,897,000
Impaired balance	0	0
Loans	20,039,000	12,500,000	12,897,000
Residential Construction [Member] \| Real Estate Portfolio Segment [Member] \| Financial Asset Acquired with Credit Deterioration [Member]
Related allowance
Impaired balance
Residential [Member] \| Real Estate Portfolio Segment [Member]
Ending Allowance Balance, individually evaluated for impairment	48,000		20,000
Ending Allowance Balance, collectively evaluated for impairment	901,000		1,162,000
Related allowance	48,000	61,000	20,000
Ending Allowance Balance Total	957,000	1,181,000	1,182,000	968,000
Ending Loan Balance, individually evaluated for impairment	2,063,000		1,753,000
Ending Loan Balance, collectively evaluated for impairment	196,578,000		187,400,000
Impaired balance	4,096,000	4,404,000	3,903,000
Loans	198,654,000	187,714,000	189,153,000
Residential [Member] \| Real Estate Portfolio Segment [Member] \| Financial Asset Acquired with Credit Deterioration [Member]
Related allowance	8,000
Impaired balance	13,000
Farmland [Member] \| Real Estate Portfolio Segment [Member]
Ending Allowance Balance, individually evaluated for impairment	30,000		29,000
Ending Allowance Balance, collectively evaluated for impairment	693,000		701,000
Related allowance	30,000	36,000	29,000
Ending Allowance Balance Total	723,000	702,000	730,000	780,000
Ending Loan Balance, individually evaluated for impairment	2,674,000		2,103,000
Ending Loan Balance, collectively evaluated for impairment	71,630,000		67,966,000
Impaired balance	2,985,000	2,416,000	2,431,000
Loans	74,341,000	62,709,000	70,069,000
Farmland [Member] \| Real Estate Portfolio Segment [Member] \| Financial Asset Acquired with Credit Deterioration [Member]
Related allowance	0
Impaired balance	37,000
Consumer [Member] \| Consumer and Other Portfolio Segment [Member]
Ending Allowance Balance, individually evaluated for impairment			0
Ending Allowance Balance, collectively evaluated for impairment	99,000		93,000
Related allowance	0	0	0
Ending Allowance Balance Total	99,000	86,000	93,000	34,000
Ending Loan Balance, individually evaluated for impairment			0
Ending Loan Balance, collectively evaluated for impairment	22,756,000		18,623,000
Impaired balance	128,000	213,000	175,000
Loans	22,756,000	18,485,000	18,623,000
Consumer [Member] \| Consumer and Other Portfolio Segment [Member] \| Financial Asset Acquired with Credit Deterioration [Member]
Related allowance	0
Impaired balance	0
Other [Member] \| Consumer and Other Portfolio Segment [Member]
Ending Allowance Balance, individually evaluated for impairment			0
Ending Allowance Balance, collectively evaluated for impairment	42,000		28,000
Related allowance	0	0	0
Ending Allowance Balance Total	42,000	10,000	28,000	$ 3,000
Ending Loan Balance, individually evaluated for impairment			0
Ending Loan Balance, collectively evaluated for impairment	21,260,000		17,016,000
Impaired balance	0	4,000	0
Loans	21,260,000	$ 5,027,000	$ 17,016,000
Other [Member] \| Consumer and Other Portfolio Segment [Member] \| Financial Asset Acquired with Credit Deterioration [Member]
Related allowance
Impaired balance

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

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