Note 3 - Loans and Allowance for Loan Losses - Recorded Investments in Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Principal loan balance	$ 409,870	$ 412,211
Accrued interest receivable	1,308	1,365
Deferred loan origination fees, net	1,040	1,041
Recorded investment in loans	412,218	414,617
Recorded Investment in Loans as Evaluated for Impairment:
Individually evaluated for impairment	3,680	3,423
Collectively evaluated for impairment	408,138	410,796
Recorded investment in loans	412,218	414,617
Principal loan balance	409,870	412,211
Accrued interest receivable	1,308	1,365
Deferred loan origination fees, net	1,040	1,041
Financial Asset Acquired with Credit Deterioration [Member]
Recorded investment in loans	400	398
Recorded Investment in Loans as Evaluated for Impairment:
Recorded investment in loans	400	398
Real Estate Mortgage Portfolio Segment [Member] | Real Estate Loan [Member]
Principal loan balance	134,298	136,399
Accrued interest receivable	494	474
Deferred loan origination fees, net	91	87
Recorded investment in loans	134,883	136,960
Recorded Investment in Loans as Evaluated for Impairment:
Individually evaluated for impairment	2,803	2,907
Collectively evaluated for impairment	131,727	133,703
Recorded investment in loans	134,883	136,960
Principal loan balance	134,298	136,399
Accrued interest receivable	494	474
Deferred loan origination fees, net	91	87
Real Estate Mortgage Portfolio Segment [Member] | Real Estate Loan [Member] | Financial Asset Acquired with Credit Deterioration [Member]
Recorded investment in loans	353	350
Recorded Investment in Loans as Evaluated for Impairment:
Recorded investment in loans	353	350
Real Estate Mortgage Portfolio Segment [Member] | Land Loan [Member]
Principal loan balance	21,248	18,198
Accrued interest receivable	72	94
Deferred loan origination fees, net	16	17
Recorded investment in loans	21,336	18,309
Recorded Investment in Loans as Evaluated for Impairment:
Individually evaluated for impairment	94
Collectively evaluated for impairment	21,242	18,309
Recorded investment in loans	21,336	18,309
Principal loan balance	21,248	18,198
Accrued interest receivable	72	94
Deferred loan origination fees, net	16	17
Real Estate Mortgage Portfolio Segment [Member] | Land Loan [Member] | Financial Asset Acquired with Credit Deterioration [Member]
Recorded investment in loans
Recorded Investment in Loans as Evaluated for Impairment:
Recorded investment in loans
Real Estate Mortgage Portfolio Segment [Member] | Construction Loans [Member]
Principal loan balance	25,313	20,995
Accrued interest receivable	48	49
Deferred loan origination fees, net	(7)	(10)
Recorded investment in loans	25,354	21,034
Recorded Investment in Loans as Evaluated for Impairment:
Individually evaluated for impairment
Collectively evaluated for impairment	25,354	21,034
Recorded investment in loans	25,354	21,034
Principal loan balance	25,313	20,995
Accrued interest receivable	48	49
Deferred loan origination fees, net	(7)	(10)
Real Estate Mortgage Portfolio Segment [Member] | Construction Loans [Member] | Financial Asset Acquired with Credit Deterioration [Member]
Recorded investment in loans
Recorded Investment in Loans as Evaluated for Impairment:
Recorded investment in loans
Real Estate Mortgage Portfolio Segment [Member] | Commercial Real Estate Loan [Member]
Principal loan balance	95,471	100,133
Accrued interest receivable	221	249
Deferred loan origination fees, net	(41)	(42)
Recorded investment in loans	95,651	100,340
Recorded Investment in Loans as Evaluated for Impairment:
Individually evaluated for impairment	365	401
Collectively evaluated for impairment	95,239	99,891
Recorded investment in loans	95,651	100,340
Principal loan balance	95,471	100,133
Accrued interest receivable	221	249
Deferred loan origination fees, net	(41)	(42)
Real Estate Mortgage Portfolio Segment [Member] | Commercial Real Estate Loan [Member] | Financial Asset Acquired with Credit Deterioration [Member]
Recorded investment in loans	47	48
Recorded Investment in Loans as Evaluated for Impairment:
Recorded investment in loans	47	48
Commercial Portfolio Segment [Member]
Principal loan balance	33,186	34,114
Accrued interest receivable	98	87
Deferred loan origination fees, net	1	2
Recorded investment in loans	33,285	34,203
Recorded Investment in Loans as Evaluated for Impairment:
Individually evaluated for impairment	319	42
Collectively evaluated for impairment	32,966	34,161
Recorded investment in loans	33,285	34,203
Principal loan balance	33,186	34,114
Accrued interest receivable	98	87
Deferred loan origination fees, net	1	2
Commercial Portfolio Segment [Member] | Financial Asset Acquired with Credit Deterioration [Member]
Recorded investment in loans
Recorded Investment in Loans as Evaluated for Impairment:
Recorded investment in loans
Consumer Portfolio Segment [Member] | Home Equity and Second Mortgage [Member]
Principal loan balance	49,423	49,802
Accrued interest receivable	185	189
Deferred loan origination fees, net	980	987
Recorded investment in loans	50,588	50,978
Recorded Investment in Loans as Evaluated for Impairment:
Individually evaluated for impairment	91	73
Collectively evaluated for impairment	50,497	50,905
Recorded investment in loans	50,588	50,978
Principal loan balance	49,423	49,802
Accrued interest receivable	185	189
Deferred loan origination fees, net	980	987
Consumer Portfolio Segment [Member] | Home Equity and Second Mortgage [Member] | Financial Asset Acquired with Credit Deterioration [Member]
Recorded investment in loans
Recorded Investment in Loans as Evaluated for Impairment:
Recorded investment in loans
Consumer Portfolio Segment [Member] | Other Consumer Loan [Member]
Principal loan balance	50,931	52,570
Accrued interest receivable	190	223
Deferred loan origination fees, net
Recorded investment in loans	51,121	52,793
Recorded Investment in Loans as Evaluated for Impairment:
Individually evaluated for impairment	8
Collectively evaluated for impairment	51,113	52,793
Recorded investment in loans	51,121	52,793
Principal loan balance	50,931	52,570
Accrued interest receivable	190	223
Deferred loan origination fees, net
Consumer Portfolio Segment [Member] | Other Consumer Loan [Member] | Financial Asset Acquired with Credit Deterioration [Member]
Recorded investment in loans
Recorded Investment in Loans as Evaluated for Impairment:
Recorded investment in loans