Note 4 - Loans - Performing and Non-performing Loan Delinquency Status (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Loans past due	$ 756,906	$ 728,758
Performing Financial Instruments [Member]
Loans past due	754,264	726,524
Nonperforming Financial Instruments [Member]
Loans past due	2,642	2,234
Real Estate Loan [Member] | Performing Financial Instruments [Member]
Loans past due	431,230	404,450
Real Estate Loan [Member] | Nonperforming Financial Instruments [Member]
Loans past due	1,623	1,997
Residential Portfolio Segment [Member] | Real Estate Loan [Member] | Performing Financial Instruments [Member]
Loans past due	151,735	143,478
Residential Portfolio Segment [Member] | Real Estate Loan [Member] | Nonperforming Financial Instruments [Member]
Loans past due	522	782
Commercial Real Estate Portfolio Segment [Member] | Real Estate Loan [Member] | Performing Financial Instruments [Member]
Loans past due	252,690	242,860
Construction, Land Acquisition and Development [Member] | Real Estate Loan [Member] | Performing Financial Instruments [Member]
Loans past due	26,805	18,112
Construction, Land Acquisition and Development [Member] | Real Estate Loan [Member] | Nonperforming Financial Instruments [Member]
Loans past due	0	245
Commercial and Industrial [Member] | Performing Financial Instruments [Member]
Loans past due	145,259	150,694
Commercial and Industrial [Member] | Nonperforming Financial Instruments [Member]
Loans past due	789	64
Consumer Portfolio Segment [Member] | Performing Financial Instruments [Member]
Loans past due	138,504	127,671
Consumer Portfolio Segment [Member] | Nonperforming Financial Instruments [Member]
Loans past due	230	173
State and Political Subdivisions [Member] | Performing Financial Instruments [Member]
Loans past due	39,271	43,709
State and Political Subdivisions [Member] | Nonperforming Financial Instruments [Member]
Loans past due	0	0
Commercial Portfolio Segment [Member] | Real Estate Loan [Member] | Nonperforming Financial Instruments [Member]
Loans past due	1,101	970
Financing Receivables, 1 to 29 Days Past Due [Member]
Loans past due	751,829	723,246
Financing Receivables, 1 to 29 Days Past Due [Member] | Performing Financial Instruments [Member]
Loans past due	750,773	722,813
Financing Receivables, 1 to 29 Days Past Due [Member] | Nonperforming Financial Instruments [Member]
Loans past due	1,056	433
Financing Receivables, 1 to 29 Days Past Due [Member] | Real Estate Loan [Member] | Performing Financial Instruments [Member]
Loans past due	429,380	402,385
Financing Receivables, 1 to 29 Days Past Due [Member] | Real Estate Loan [Member] | Nonperforming Financial Instruments [Member]
Loans past due	230	377
Financing Receivables, 1 to 29 Days Past Due [Member] | Residential Portfolio Segment [Member] | Real Estate Loan [Member] | Performing Financial Instruments [Member]
Loans past due	151,136	143,142
Financing Receivables, 1 to 29 Days Past Due [Member] | Residential Portfolio Segment [Member] | Real Estate Loan [Member] | Nonperforming Financial Instruments [Member]
Loans past due	230	176
Financing Receivables, 1 to 29 Days Past Due [Member] | Commercial Real Estate Portfolio Segment [Member] | Real Estate Loan [Member] | Performing Financial Instruments [Member]
Loans past due	251,467	241,477
Financing Receivables, 1 to 29 Days Past Due [Member] | Construction, Land Acquisition and Development [Member] | Real Estate Loan [Member] | Performing Financial Instruments [Member]
Loans past due	26,777	17,766
Financing Receivables, 1 to 29 Days Past Due [Member] | Construction, Land Acquisition and Development [Member] | Real Estate Loan [Member] | Nonperforming Financial Instruments [Member]
Loans past due	0	0
Financing Receivables, 1 to 29 Days Past Due [Member] | Commercial and Industrial [Member] | Performing Financial Instruments [Member]
Loans past due	144,896	150,378
Financing Receivables, 1 to 29 Days Past Due [Member] | Commercial and Industrial [Member] | Nonperforming Financial Instruments [Member]
Loans past due	750	0
Financing Receivables, 1 to 29 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Performing Financial Instruments [Member]
Loans past due	137,235	126,341
Financing Receivables, 1 to 29 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Nonperforming Financial Instruments [Member]
Loans past due	76	56
Financing Receivables, 1 to 29 Days Past Due [Member] | State and Political Subdivisions [Member] | Performing Financial Instruments [Member]
Loans past due	39,262	43,709
Financing Receivables, 1 to 29 Days Past Due [Member] | State and Political Subdivisions [Member] | Nonperforming Financial Instruments [Member]
Loans past due	0	0
Financing Receivables, 1 to 29 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Real Estate Loan [Member] | Nonperforming Financial Instruments [Member]
Loans past due		201
Financing Receivables, 30 to 59 Days Past Due [Member]
Loans past due	2,109	3,237
Financing Receivables, 30 to 59 Days Past Due [Member] | Performing Financial Instruments [Member]
Loans past due	2,091	2,742
Financing Receivables, 30 to 59 Days Past Due [Member] | Nonperforming Financial Instruments [Member]
Loans past due	18	495
Financing Receivables, 30 to 59 Days Past Due [Member] | Real Estate Loan [Member] | Performing Financial Instruments [Member]
Loans past due	818	1,405
Financing Receivables, 30 to 59 Days Past Due [Member] | Real Estate Loan [Member] | Nonperforming Financial Instruments [Member]
Loans past due	0	470
Financing Receivables, 30 to 59 Days Past Due [Member] | Residential Portfolio Segment [Member] | Real Estate Loan [Member] | Performing Financial Instruments [Member]
Loans past due	271	229
Financing Receivables, 30 to 59 Days Past Due [Member] | Residential Portfolio Segment [Member] | Real Estate Loan [Member] | Nonperforming Financial Instruments [Member]
Loans past due	0	202
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Real Estate Portfolio Segment [Member] | Real Estate Loan [Member] | Performing Financial Instruments [Member]
Loans past due	519	830
Financing Receivables, 30 to 59 Days Past Due [Member] | Construction, Land Acquisition and Development [Member] | Real Estate Loan [Member] | Performing Financial Instruments [Member]
Loans past due	28	346
Financing Receivables, 30 to 59 Days Past Due [Member] | Construction, Land Acquisition and Development [Member] | Real Estate Loan [Member] | Nonperforming Financial Instruments [Member]
Loans past due	0	245
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial and Industrial [Member] | Performing Financial Instruments [Member]
Loans past due	272	307
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial and Industrial [Member] | Nonperforming Financial Instruments [Member]
Loans past due	0	0
Financing Receivables, 30 to 59 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Performing Financial Instruments [Member]
Loans past due	992	1,030
Financing Receivables, 30 to 59 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Nonperforming Financial Instruments [Member]
Loans past due	18	25
Financing Receivables, 30 to 59 Days Past Due [Member] | State and Political Subdivisions [Member] | Performing Financial Instruments [Member]
Loans past due	9	0
Financing Receivables, 30 to 59 Days Past Due [Member] | State and Political Subdivisions [Member] | Nonperforming Financial Instruments [Member]
Loans past due	0	0
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Real Estate Loan [Member] | Nonperforming Financial Instruments [Member]
Loans past due	0	23
Financing Receivables, 60 to 89 Days Past Due [Member]
Loans past due	1,597	988
Financing Receivables, 60 to 89 Days Past Due [Member] | Performing Financial Instruments [Member]
Loans past due	1,400	969
Financing Receivables, 60 to 89 Days Past Due [Member] | Nonperforming Financial Instruments [Member]
Loans past due	197	19
Financing Receivables, 60 to 89 Days Past Due [Member] | Real Estate Loan [Member] | Performing Financial Instruments [Member]
Loans past due	1,032	660
Financing Receivables, 60 to 89 Days Past Due [Member] | Real Estate Loan [Member] | Nonperforming Financial Instruments [Member]
Loans past due	191	17
Financing Receivables, 60 to 89 Days Past Due [Member] | Residential Portfolio Segment [Member] | Real Estate Loan [Member] | Performing Financial Instruments [Member]
Loans past due	328	107
Financing Receivables, 60 to 89 Days Past Due [Member] | Residential Portfolio Segment [Member] | Real Estate Loan [Member] | Nonperforming Financial Instruments [Member]
Loans past due	191	17
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Real Estate Portfolio Segment [Member] | Real Estate Loan [Member] | Performing Financial Instruments [Member]
Loans past due	704	553
Financing Receivables, 60 to 89 Days Past Due [Member] | Construction, Land Acquisition and Development [Member] | Real Estate Loan [Member] | Performing Financial Instruments [Member]
Loans past due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member] | Construction, Land Acquisition and Development [Member] | Real Estate Loan [Member] | Nonperforming Financial Instruments [Member]
Loans past due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial and Industrial [Member] | Performing Financial Instruments [Member]
Loans past due	91	9
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial and Industrial [Member] | Nonperforming Financial Instruments [Member]
Loans past due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Performing Financial Instruments [Member]
Loans past due	277	300
Financing Receivables, 60 to 89 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Nonperforming Financial Instruments [Member]
Loans past due	6	2
Financing Receivables, 60 to 89 Days Past Due [Member] | State and Political Subdivisions [Member] | Performing Financial Instruments [Member]
Loans past due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member] | State and Political Subdivisions [Member] | Nonperforming Financial Instruments [Member]
Loans past due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Real Estate Loan [Member] | Nonperforming Financial Instruments [Member]
Loans past due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans past due	1,371	1,287
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Performing Financial Instruments [Member]
Loans past due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Nonperforming Financial Instruments [Member]
Loans past due	1,371	1,287
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Real Estate Loan [Member] | Performing Financial Instruments [Member]
Loans past due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Real Estate Loan [Member] | Nonperforming Financial Instruments [Member]
Loans past due	1,202	1,133
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Residential Portfolio Segment [Member] | Real Estate Loan [Member] | Performing Financial Instruments [Member]
Loans past due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Residential Portfolio Segment [Member] | Real Estate Loan [Member] | Nonperforming Financial Instruments [Member]
Loans past due	101	387
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial Real Estate Portfolio Segment [Member] | Real Estate Loan [Member] | Performing Financial Instruments [Member]
Loans past due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Construction, Land Acquisition and Development [Member] | Real Estate Loan [Member] | Performing Financial Instruments [Member]
Loans past due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Construction, Land Acquisition and Development [Member] | Real Estate Loan [Member] | Nonperforming Financial Instruments [Member]
Loans past due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial and Industrial [Member] | Performing Financial Instruments [Member]
Loans past due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial and Industrial [Member] | Nonperforming Financial Instruments [Member]
Loans past due	39	64
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Performing Financial Instruments [Member]
Loans past due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Nonperforming Financial Instruments [Member]
Loans past due	130	90
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | State and Political Subdivisions [Member] | Performing Financial Instruments [Member]
Loans past due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | State and Political Subdivisions [Member] | Nonperforming Financial Instruments [Member]
Loans past due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Real Estate Loan [Member] | Nonperforming Financial Instruments [Member]
Loans past due	$ 1,101	$ 746