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Note 4 - Loans and Allowance for Loan Losses - Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2020	Dec. 31, 2019
Beginning balance				$ 5,061				$ 4,065				$ 3,634	$ 5,061	$ 4,065	$ 3,634
Provisions	$ 225	$ 400	$ 825	351	$ 450	$ 225	$ 300	450	$ 200	$ 455	$ 316	197	1,801	1,425	1,168
Charge-offs													(511)	(766)	(1,027)
Recoveries													274	337	290
Ending balance	6,625				5,061				4,065				6,625	5,061	4,065
Individually evaluated for impairment																$ 0	$ 16
Collectively evaluated for impairment																6,594	5,033
Ending balance	6,625			5,061	5,061			4,065	4,065			3,634	5,061	4,065	3,634	6,625	5,061
Individually evaluated for impairment																3,168	2,747
Collectively evaluated for impairment																505,414	470,116
Recorded investment in loans																508,879	473,187
Financial Asset Acquired with Credit Deterioration [Member]
Beginning balance				12									12
Ending balance	31				12								31	12
Ending balance	31			12	12								12	12		31	12
Recorded investment in loans																297	324
Real Estate Mortgage Portfolio Segment [Member] \| Residential Loan [Member]
Beginning balance				867				693				219	867	693	219
Provisions													393	251	723
Charge-offs													(72)	(194)	(258)
Recoveries													51	117	9
Ending balance	1,239				867				693				1,239	867	693
Individually evaluated for impairment																0	16
Collectively evaluated for impairment																1,208	839
Ending balance	1,239			867	867			693	693			219	1,239	693	219	1,239	867
Individually evaluated for impairment																1,728	1,926
Collectively evaluated for impairment																129,851	130,328
Recorded investment in loans																131,850	132,539
Real Estate Mortgage Portfolio Segment [Member] \| Residential Loan [Member] \| Financial Asset Acquired with Credit Deterioration [Member]
Beginning balance				12									12
Ending balance	31				12								31	12
Ending balance	31			12	12								12	12		31	12
Recorded investment in loans																271	285
Real Estate Mortgage Portfolio Segment [Member] \| Land Loan [Member]
Beginning balance				163				162				133	163	162	133
Provisions													46	0	29
Charge-offs													0	0	0
Recoveries													0	1	0
Ending balance	209				163				162				209	163	162
Individually evaluated for impairment																0	0
Collectively evaluated for impairment																209	163
Ending balance	209			163	163			162	162			133	209	162	133	209	163
Individually evaluated for impairment																97	115
Collectively evaluated for impairment																17,364	19,199
Recorded investment in loans																17,461	19,314
Real Estate Mortgage Portfolio Segment [Member] \| Land Loan [Member] \| Financial Asset Acquired with Credit Deterioration [Member]
Beginning balance				0									0
Ending balance	0				0								0	0
Ending balance	0			0	0								0	0		0	0
Recorded investment in loans																0	0
Real Estate Mortgage Portfolio Segment [Member] \| Construction Loans [Member]
Beginning balance				350				224				245	350	224	245
Provisions													(58)	126	(21)
Charge-offs													0	0	0
Recoveries													0	0	0
Ending balance	292				350				224				292	350	224
Individually evaluated for impairment																0	0
Collectively evaluated for impairment																292	350
Ending balance	292			350	350			224	224			245	292	224	245	292	350
Individually evaluated for impairment																0	0
Collectively evaluated for impairment																25,018	32,644
Recorded investment in loans																25,018	32,644
Real Estate Mortgage Portfolio Segment [Member] \| Construction Loans [Member] \| Financial Asset Acquired with Credit Deterioration [Member]
Beginning balance				0									0
Ending balance	0				0								0	0
Ending balance	0			0	0								0	0		0	0
Recorded investment in loans																0	0
Real Estate Mortgage Portfolio Segment [Member] \| Commercial Real Estate Loan [Member]
Beginning balance				1,623				1,401				1,622	1,623	1,401	1,622
Provisions													735	222	(296)
Charge-offs													0	0	0
Recoveries													0	0	75
Ending balance	2,358				1,623				1,401				2,358	1,623	1,401
Individually evaluated for impairment																0	0
Collectively evaluated for impairment																2,358	1,623
Ending balance	2,358			1,623	1,623			1,401	1,401			1,622	2,358	1,401	1,622	2,358	1,623
Individually evaluated for impairment																779	353
Collectively evaluated for impairment																134,679	121,421
Recorded investment in loans																135,484	121,813
Real Estate Mortgage Portfolio Segment [Member] \| Commercial Real Estate Loan [Member] \| Financial Asset Acquired with Credit Deterioration [Member]
Beginning balance				0									0
Ending balance	0				0								0	0
Ending balance	0			0	0								0	0		0	0
Recorded investment in loans																26	39
Commercial Portfolio Segment [Member]
Beginning balance				595				459				291	595	459	291
Provisions													280	132	218
Charge-offs													(32)	0	(51)
Recoveries													0	4	1
Ending balance	843				595				459				843	595	459
Individually evaluated for impairment																0	0
Collectively evaluated for impairment																843	595
Ending balance	843			595	595			459	459			291	843	459	291	843	595
Individually evaluated for impairment																211	249
Collectively evaluated for impairment																81,598	45,200
Recorded investment in loans																81,809	45,449
Commercial Portfolio Segment [Member] \| Financial Asset Acquired with Credit Deterioration [Member]
Beginning balance				0									0
Ending balance	0				0								0	0
Ending balance	0			0	0								0	0		0	0
Recorded investment in loans																0	0
Consumer Portfolio Segment [Member] \| Home Equity and Second Mortgage [Member]
Beginning balance				515				443				710	515	443	710
Provisions													91	77	(278)
Charge-offs													0	(24)	(21)
Recoveries													11	19	32
Ending balance	617				515				443				617	515	443
Individually evaluated for impairment																0	0
Collectively evaluated for impairment																617	515
Ending balance	617			515	515			443	443			710	617	443	710	617	515
Individually evaluated for impairment																353	56
Collectively evaluated for impairment																52,924	55,932
Recorded investment in loans																53,277	55,988
Consumer Portfolio Segment [Member] \| Home Equity and Second Mortgage [Member] \| Financial Asset Acquired with Credit Deterioration [Member]
Beginning balance				0									0
Ending balance	0				0								0	0
Ending balance	0			0	0								0	0		0	0
Recorded investment in loans																0	0
Consumer Portfolio Segment [Member] \| All Other Consumer Excluding Home Equity and Second Mortgage [Member]
Beginning balance				948				683					948	683
Provisions													314	617
Charge-offs													(407)	(548)
Recoveries													212	196
Ending balance	1,067				948				683				1,067	948	683
Individually evaluated for impairment																0	0
Collectively evaluated for impairment																1,067	948
Ending balance	1,067			948	948			683	683				1,067	683	683	1,067	948
Individually evaluated for impairment																0	48
Collectively evaluated for impairment																63,980	65,392
Recorded investment in loans																63,980	65,440
Consumer Portfolio Segment [Member] \| All Other Consumer Excluding Home Equity and Second Mortgage [Member] \| Financial Asset Acquired with Credit Deterioration [Member]
Beginning balance				0									0
Ending balance	0				0								0	0
Ending balance	$ 0			$ 0	$ 0								$ 0	0		0	0
Recorded investment in loans																0	0
Consumer Portfolio Segment [Member] \| Other Consumer Loan [Member]
Beginning balance								683				414		683	414
Provisions															793
Charge-offs															(697)
Recoveries															173
Ending balance									683						683
Ending balance								$ 683	$ 683			$ 414		$ 683	$ 683
Recorded investment in loans																$ 63,980	$ 65,440