Note 5 - Loans and the Allowance for Loan Losses - Allocation of the Allowance for Loan Losses (Details) - USD ($)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Balance, beginning of year	$ 6,958,000	$ 6,669,000	$ 6,549,000
Charge-offs	(1,521,000)	(1,191,000)	(879,000)
Recoveries	306,000	480,000	399,000
Provision	1,500,000	1,000,000	600,000
Balance, end of year	7,243,000	6,958,000	6,669,000
Allowance for loan losses, individually evaluated for impairment	154,000	181,000
Allowance for loan losses, collectively evaluated for impairment	7,089,000	6,777,000
Loans, individually evaluated for impairment	2,244,000	1,275,000
Loans, collectively evaluated for impairment	617,474,000	564,924,000
Loans	619,718,000	566,199,000
Commercial Portfolio Segment [Member] \| Commercial Loans [Member]
Balance, beginning of year	914,000	725,000	655,000
Charge-offs	(587,000)	(325,000)	(202,000)
Recoveries	26,000	83,000	89,000
Provision	264,000	431,000	183,000
Balance, end of year	617,000	914,000	725,000
Allowance for loan losses, individually evaluated for impairment		128,000
Allowance for loan losses, collectively evaluated for impairment	617,000	786,000
Loans, individually evaluated for impairment	25,000	128,000
Loans, collectively evaluated for impairment	47,867,000	49,435,000
Loans	47,892,000	49,563,000
Commercial Portfolio Segment [Member] \| Agricultural Loans [Member]
Balance, beginning of year	538,000	623,000	466,000
Charge-offs
Recoveries
Provision	115,000	(85,000)	157,000
Balance, end of year	653,000	538,000	623,000
Allowance for loan losses, individually evaluated for impairment
Allowance for loan losses, collectively evaluated for impairment	653,000	538,000
Loans, individually evaluated for impairment	248,000	250,000
Loans, collectively evaluated for impairment	78,537,000	68,910,000
Loans	78,785,000	69,160,000
Commercial Portfolio Segment [Member] \| Real Estate Loan [Member]
Balance, beginning of year	2,686,000	2,729,000	2,740,000
Charge-offs			(48,000)
Recoveries	4,000	21,000	115,000
Provision	736,000	(64,000)	(78,000)
Balance, end of year	3,426,000	2,686,000	2,729,000
Allowance for loan losses, individually evaluated for impairment	121,000
Allowance for loan losses, collectively evaluated for impairment	3,305,000	2,686,000
Loans, individually evaluated for impairment	815,000	131,000
Loans, collectively evaluated for impairment	316,171,000	271,579,000
Loans	316,986,000	271,710,000
Commercial Portfolio Segment [Member] \| Construction Loans [Member]
Balance, beginning of year	758,000	783,000	927,000
Charge-offs
Recoveries		3,000
Provision	(277,000)	(28,000)	(144,000)
Balance, end of year	481,000	758,000	783,000
Allowance for loan losses, individually evaluated for impairment	5,000	12,000
Allowance for loan losses, collectively evaluated for impairment	476,000	746,000
Loans, individually evaluated for impairment	110,000	117,000
Loans, collectively evaluated for impairment	31,071,000	40,044,000
Loans	31,181,000	40,161,000
Residential Portfolio Segment [Member] \| Real Estate Loan [Member]
Balance, beginning of year	214,000	231,000	280,000
Charge-offs		(25,000)
Recoveries	3,000	93,000	3,000
Provision	(54,000)	(85,000)	(52,000)
Balance, end of year	163,000	214,000	231,000
Allowance for loan losses, individually evaluated for impairment	28,000	41,000
Allowance for loan losses, collectively evaluated for impairment	135,000	173,000
Loans, individually evaluated for impairment	612,000	649,000
Loans, collectively evaluated for impairment	13,918,000	15,251,000
Loans	14,530,000	15,900,000
Residential Portfolio Segment [Member] \| Equity Lines of Credit [Member]
Balance, beginning of year	464,000	533,000	575,000
Charge-offs	(6,000)		(121,000)
Recoveries	5,000	5,000	4,000
Provision	(70,000)	(74,000)	75,000
Balance, end of year	393,000	464,000	533,000
Allowance for loan losses, individually evaluated for impairment
Allowance for loan losses, collectively evaluated for impairment	393,000	464,000
Loans, individually evaluated for impairment	434,000
Loans, collectively evaluated for impairment	35,037,000	38,490,000
Loans	35,471,000	38,490,000
Consumer Portfolio Segment [Member] \| Automobile Loan [Member]
Balance, beginning of year	1,289,000	946,000	815,000
Charge-offs	(867,000)	(801,000)	(450,000)
Recoveries	258,000	256,000	173,000
Provision	729,000	888,000	408,000
Balance, end of year	1,409,000	1,289,000	946,000
Allowance for loan losses, individually evaluated for impairment
Allowance for loan losses, collectively evaluated for impairment	1,409,000	1,289,000
Loans, individually evaluated for impairment
Loans, collectively evaluated for impairment	90,310,000	77,135,000
Loans	90,310,000	77,135,000
Consumer Portfolio Segment [Member] \| Other Loans [Member]
Balance, beginning of year	95,000	99,000	91,000
Charge-offs	(61,000)	(40,000)	(58,000)
Recoveries	10,000	19,000	15,000
Provision	57,000	17,000	51,000
Balance, end of year	101,000	95,000	$ 99,000
Allowance for loan losses, individually evaluated for impairment
Allowance for loan losses, collectively evaluated for impairment	101,000	95,000
Loans, individually evaluated for impairment
Loans, collectively evaluated for impairment	4,563,000	4,080,000
Loans	$ 4,563,000	$ 4,080,000

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 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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