Note 4 - Loans and the Allowance for Loan Losses - Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Balance, beginning of period	$ 6,958	$ 6,669	$ 6,669
Provision charged to operations	400	200	1,000
Losses charged to allowance	(351)	(449)	(1,191)
Recoveries	60	202	480
Balance, end of period	7,067	6,622	6,958
Charge-offs	(351)	(449)	(1,191)
Provision	400	200	1,000
Allowance for loan losses, individually evaluated for impairment	229		181
Allowance for loan losses, collectively evaluated for impairment	6,838		6,777
Loans, individually evaluated for impairment	1,738		1,275
Loans, collectively evaluated for impairment	571,708		564,924
Loans	573,446		566,199
Commercial Portfolio Segment [Member] \| Commercial Loans [Member]
Balance, beginning of period	914	725	725
Provision charged to operations	(111)	305
Losses charged to allowance	(16)	(265)
Recoveries	9	7
Balance, end of period	796	772	914
Charge-offs	(16)	(265)
Provision	(111)	305
Allowance for loan losses, individually evaluated for impairment	123		128
Allowance for loan losses, collectively evaluated for impairment	673		786
Loans, individually evaluated for impairment	123		128
Loans, collectively evaluated for impairment	42,584		49,435
Loans	42,707		49,563
Commercial Portfolio Segment [Member] \| Agricultural Loans [Member]
Balance, beginning of period	538	623	623
Provision charged to operations	4	(129)
Losses charged to allowance
Recoveries
Balance, end of period	542	494	538
Charge-offs
Provision	4	(129)
Allowance for loan losses, individually evaluated for impairment
Allowance for loan losses, collectively evaluated for impairment	542		538
Loans, individually evaluated for impairment	250		250
Loans, collectively evaluated for impairment	69,791		68,910
Loans	70,041		69,160
Commercial Portfolio Segment [Member] \| Real Estate Loan [Member]
Balance, beginning of period	2,686	2,729	2,729
Provision charged to operations	283	13
Losses charged to allowance
Recoveries		17
Balance, end of period	2,969	2,759	2,686
Charge-offs
Provision	283	13
Allowance for loan losses, individually evaluated for impairment	61
Allowance for loan losses, collectively evaluated for impairment	2,908		2,686
Loans, individually evaluated for impairment	611		131
Loans, collectively evaluated for impairment	281,922		271,579
Loans	282,533		271,710
Commercial Portfolio Segment [Member] \| Construction Loans [Member]
Balance, beginning of period	758	783	783
Provision charged to operations	(117)	6
Losses charged to allowance
Recoveries		2
Balance, end of period	641	791	758
Charge-offs
Provision	(117)	6
Allowance for loan losses, individually evaluated for impairment	10		12
Allowance for loan losses, collectively evaluated for impairment	631		746
Loans, individually evaluated for impairment	115		117
Loans, collectively evaluated for impairment	37,522		40,044
Loans	37,637		40,161
Residential Portfolio Segment [Member] \| Real Estate Loan [Member]
Balance, beginning of period	214	231	231
Provision charged to operations	(20)	(110)
Losses charged to allowance
Recoveries	1	91
Balance, end of period	195	212	214
Charge-offs
Provision	(20)	(110)
Allowance for loan losses, individually evaluated for impairment	35		41
Allowance for loan losses, collectively evaluated for impairment	160		173
Loans, individually evaluated for impairment	639		649
Loans, collectively evaluated for impairment	15,774		15,251
Loans	16,413		15,900
Residential Portfolio Segment [Member] \| Equity Lines of Credit [Member]
Balance, beginning of period	464	533	533
Provision charged to operations	(15)	(24)
Losses charged to allowance
Recoveries	1	1
Balance, end of period	450	510	464
Charge-offs
Provision	(15)	(24)
Allowance for loan losses, individually evaluated for impairment
Allowance for loan losses, collectively evaluated for impairment	450		464
Loans, individually evaluated for impairment
Loans, collectively evaluated for impairment	37,519		38,490
Loans	37,519		38,490
Consumer Portfolio Segment [Member] \| Automobile Loan [Member]
Balance, beginning of period	1,289	946	946
Provision charged to operations	360	114
Losses charged to allowance	(312)	(165)
Recoveries	47	82
Balance, end of period	1,384	977	1,289
Charge-offs	(312)	(165)
Provision	360	114
Allowance for loan losses, individually evaluated for impairment
Allowance for loan losses, collectively evaluated for impairment	1,384		1,289
Loans, individually evaluated for impairment
Loans, collectively evaluated for impairment	82,737		77,135
Loans	82,737		77,135
Consumer Portfolio Segment [Member] \| Other Loans [Member]
Balance, beginning of period	95	99	99
Provision charged to operations	16	25
Losses charged to allowance	(23)	(19)
Recoveries	2	2
Balance, end of period	90	107	95
Charge-offs	(23)	(19)
Provision	16	$ 25
Allowance for loan losses, individually evaluated for impairment
Allowance for loan losses, collectively evaluated for impairment	90		95
Loans, individually evaluated for impairment
Loans, collectively evaluated for impairment	3,859		4,080
Loans	$ 3,859		$ 4,080

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

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

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Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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The balance of financing receivables 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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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Amount of expense related to estimated loss from loan and lease transactions.

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