Note 4 - Loans and the Allowance for Loan Losses - Allocation of the Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Sep. 30, 2020	Dec. 31, 2019
Beginning balance	$ 8,835	$ 7,058	$ 7,243	$ 6,958	$ 6,958
Charge-offs	(133)	(217)	(668)	(874)	(1,521)
Recoveries	98	85	225	242	306
Provision	800	300	2,800	900	1,500
Ending balance	9,600	7,226	9,600	7,226	7,243
Charge-offs	(133)	(217)	(668)	(874)	(1,521)
Allowance for loan losses, individually evaluated for impairment						$ 153	$ 154
Allowance for loan losses, collectively evaluated for impairment						9,447	7,089
Ending balance	8,835	7,058	7,243	7,226	6,958	9,600	7,243
Loans, individually evaluated for impairment						2,083	2,244
Loans, collectively evaluated for impairment						745,802	617,474
Loans						747,885	619,718
Commercial Portfolio Segment [Member] | Commercial Loans [Member]
Beginning balance	788	721	617	914	914
Charge-offs	0	(49)	(131)	(186)
Recoveries	14	5	21	21
Provision	155	86	450	14
Ending balance	957	763	957	763	617
Charge-offs	0	(49)	(131)	(186)
Allowance for loan losses, individually evaluated for impairment						0	0
Allowance for loan losses, collectively evaluated for impairment						957	617
Ending balance	788	721	957	763	914	957	617
Loans, individually evaluated for impairment						0	25
Loans, collectively evaluated for impairment						167,770	47,867
Loans						167,770	47,892
Commercial Portfolio Segment [Member] | Agricultural Loans [Member]
Beginning balance	691	627	653	538	538
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provision	55	34	93	123
Ending balance	746	661	746	661	653
Charge-offs	0	0	0	0
Allowance for loan losses, individually evaluated for impairment						0	0
Allowance for loan losses, collectively evaluated for impairment						746	653
Ending balance	691	627	746	661	538	746	653
Loans, individually evaluated for impairment						245	248
Loans, collectively evaluated for impairment						73,964	78,537
Loans						74,209	78,785
Commercial Portfolio Segment [Member] | Real Estate Loan [Member]
Beginning balance	4,405	2,997	3,426	2,686	2,686
Charge-offs	0	0	0	0
Recoveries	3	2	6	2
Provision	369	88	1,345	399
Ending balance	4,777	3,087	4,777	3,087	3,426
Charge-offs	0	0	0	0
Allowance for loan losses, individually evaluated for impairment						122	121
Allowance for loan losses, collectively evaluated for impairment						4,655	3,305
Ending balance	4,405	2,997	4,777	3,087	2,686	4,777	3,426
Loans, individually evaluated for impairment						786	815
Loans, collectively evaluated for impairment						332,982	316,171
Loans						333,768	316,986
Commercial Portfolio Segment [Member] | Construction Loans [Member]
Beginning balance	476	597	481	758	758
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provision	92	43	87	(118)
Ending balance	568	640	568	640	481
Charge-offs	0	0	0	0
Allowance for loan losses, individually evaluated for impairment						5	5
Allowance for loan losses, collectively evaluated for impairment						563	476
Ending balance	476	597	568	640	758	568	481
Loans, individually evaluated for impairment						108	110
Loans, collectively evaluated for impairment						27,778	31,071
Loans						27,886	31,181
Residential Portfolio Segment [Member] | Real Estate Loan [Member]
Beginning balance	173	177	163	214	214
Charge-offs	0	0	0	0
Recoveries	1	0	3	2
Provision	0	(3)	8	(42)
Ending balance	174	174	174	174	163
Charge-offs	0	0	0	0
Allowance for loan losses, individually evaluated for impairment						26	28
Allowance for loan losses, collectively evaluated for impairment						148	135
Ending balance	173	177	174	174	214	174	163
Loans, individually evaluated for impairment						649	612
Loans, collectively evaluated for impairment						12,199	13,918
Loans						12,848	14,530
Residential Portfolio Segment [Member] | Equity Lines of Credit [Member]
Beginning balance	474	468	393	464	464
Charge-offs	0	(1)	0	(6)
Recoveries	1	2	3	4
Provision	15	(36)	94	(29)
Ending balance	490	433	490	433	393
Charge-offs	0	(1)	0	(6)
Allowance for loan losses, individually evaluated for impairment						0	0
Allowance for loan losses, collectively evaluated for impairment						490	393
Ending balance	474	468	490	433	464	490	393
Loans, individually evaluated for impairment						295	434
Loans, collectively evaluated for impairment						34,599	35,037
Loans						34,894	35,471
Consumer Portfolio Segment [Member] | Automobile Loan [Member]
Beginning balance	1,712	1,372	1,409	1,289	1,289
Charge-offs	(94)	(140)	(457)	(624)
Recoveries	78	72	185	207
Provision	83	62	642	494
Ending balance	1,779	1,366	1,779	1,366	1,409
Charge-offs	(94)	(140)	(457)	(624)
Allowance for loan losses, individually evaluated for impairment						0	0
Allowance for loan losses, collectively evaluated for impairment						1,779	1,409
Ending balance	1,712	1,372	1,779	1,366	1,289	1,779	1,409
Loans, individually evaluated for impairment						0	0
Loans, collectively evaluated for impairment						92,248	90,310
Loans						92,248	90,310
Consumer Portfolio Segment [Member] | Other Loans [Member]
Beginning balance	116	99	101	95	95
Charge-offs	(39)	(27)	(80)	(58)
Recoveries	1	4	7	6
Provision	31	26	81	59
Ending balance	109	102	109	102	101
Charge-offs	(39)	(27)	(80)	(58)
Allowance for loan losses, individually evaluated for impairment						0	0
Allowance for loan losses, collectively evaluated for impairment						109	101
Ending balance	$ 116	$ 99	$ 109	$ 102	$ 95	109	101
Loans, individually evaluated for impairment						0	0
Loans, collectively evaluated for impairment						4,262	4,563
Loans						$ 4,262	$ 4,563