Note 4 - Loans and Allowance for Loan Losses - Loans Individually Evaluated for Impairment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Allowance for Loan Losses Allocated	$ 90		$ 90		$ 94
Unpaid principal balance	18,084		18,084		19,917
Recorded investment	16,257		16,257		18,108
Average impaired loans	16,138	$ 17,708	16,348	$ 17,549
Interest income recognized	182	181	386	631
Cash basis interest recognized	182	181	386	631
Commercial Real Estate Portfolio Segment [Member] | Commercial Real Estate Nonowner Occupied [Member]
Unpaid principal balance - with allowance recorded	366		366		372
Recorded investment - with allowance recorded	366		366		372
Allowance for Loan Losses Allocated	90		90		94
Unpaid principal balance - with no allowance recorded	4,198		4,198		4,989
Recorded investment - with no allowance recorded	2,776		2,776		3,534
Average impaired loans - with allowance recorded	368	379	370	380
Interest income recognized - with allowance recorded	7	5	8	14
Cash basis interest recognized - with allowance recorded	7	5	8	14
Average impaired loans - with no allowance recorded	3,037	3,779	3,131	3,730
Interest income recognized - with no allowance recorded	16	21	37	74
Cash basis interest recognized - with no allowance recorded	16	21	37	74
Commercial Real Estate Portfolio Segment [Member] | Commercial Real Estate Owner Occupied [Member]
Unpaid principal balance - with no allowance recorded	2,451		2,451		3,427
Recorded investment - with no allowance recorded	2,451		2,451		3,427
Average impaired loans - with no allowance recorded	2,465	2,836	2,478	2,921
Interest income recognized - with no allowance recorded	36	36	69	120
Cash basis interest recognized - with no allowance recorded	36	36	69	120
Commercial Real Estate Portfolio Segment [Member] | Construction Loans [Member]
Unpaid principal balance - with no allowance recorded	344		344		352
Recorded investment - with no allowance recorded
Average impaired loans - with no allowance recorded		487		501
Interest income recognized - with no allowance recorded	5	5	10	108
Cash basis interest recognized - with no allowance recorded	5	5	10	108
Residential Portfolio Segment [Member]
Unpaid principal balance - with no allowance recorded	1,688		1,688		1,420
Recorded investment - with no allowance recorded	1,627		1,627		1,420
Average impaired loans - with no allowance recorded	1,653	1,028	1,575	992
Interest income recognized - with no allowance recorded	11	12	30	20
Cash basis interest recognized - with no allowance recorded	11	12	30	20
Commercial and Industrial Portfolio Segment [Member]
Unpaid principal balance - with no allowance recorded	9,037		9,037		9,154
Recorded investment - with no allowance recorded	9,037		9,037		9,154
Average impaired loans - with no allowance recorded	8,615	8,990	8,794	8,815
Interest income recognized - with no allowance recorded	107	100	232	290
Cash basis interest recognized - with no allowance recorded	$ 107	100	$ 232	290
Consumer Portfolio Segment [Member] | Home Equity Loan [Member]
Unpaid principal balance - with allowance recorded					203
Recorded investment - with allowance recorded					$ 201
Average impaired loans - with allowance recorded		209		210
Interest income recognized - with allowance recorded		2		5
Cash basis interest recognized - with allowance recorded		$ 2		$ 5