Note 4 - Loans and Related Allowance for Loan Loss - Impaired Loans (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Recorded investment - with no related allowance	$ 5,847	$ 6,044
Unpaid principal balance - with no related allowance	5,849	6,044
Average recorded investment - with no related allowance	6,105	6,594
Interest income recognized - with no related allowance	216	310
Unpaid principal balance	9,232	9,797
Recorded investment - with related allowance	3,309	3,657
Related allowance	1,038	1,160
Unpaid principal balance - with related allowance	3,383	3,753
Average recorded investment - with related allowance	3,644	3,736
Interest income recognized - with related allowance	128	99
Impaired Loans	9,156	9,701
Average recorded investment	9,749	10,330
Interest income recognized	344	409
Originated Loans [Member]
Recorded investment - with no related allowance	3,372	3,643
Unpaid principal balance - with no related allowance	3,374	3,643
Average recorded investment - with no related allowance	3,495	3,968
Interest income recognized - with no related allowance	118	174
Unpaid principal balance	6,673	6,838
Recorded investment - with related allowance	3,225	3,189
Related allowance	1,028	1,015
Unpaid principal balance - with related allowance	3,299	3,195
Average recorded investment - with related allowance	3,541	3,228
Interest income recognized - with related allowance	124	93
Impaired Loans	6,597	6,832
Average recorded investment	7,036	7,196
Interest income recognized	242	267
Acquired Loans [Member]
Recorded investment - with no related allowance	2,475	2,401
Unpaid principal balance - with no related allowance	2,475	2,401
Average recorded investment - with no related allowance	2,610	2,626
Interest income recognized - with no related allowance	98	136
Unpaid principal balance	2,559	2,959
Recorded investment - with related allowance	84	468
Related allowance	10	145
Unpaid principal balance - with related allowance	84	558
Average recorded investment - with related allowance	103	508
Interest income recognized - with related allowance	4	6
Impaired Loans	2,559	2,869
Average recorded investment	2,713	3,134
Interest income recognized	102	142
Residential Portfolio Segment [Member] | Real Estate Sector [Member]
Recorded investment - with no related allowance	1,392	1,300
Unpaid principal balance - with no related allowance		1,300
Average recorded investment - with no related allowance	1,417	1,320
Interest income recognized - with no related allowance	52	68
Unpaid principal balance	1,394	1,300
Related allowance
Impaired Loans	1,392	1,300
Average recorded investment	1,417	1,320
Interest income recognized	52	68
Residential Portfolio Segment [Member] | Real Estate Sector [Member] | Originated Loans [Member]
Recorded investment - with no related allowance	124
Unpaid principal balance - with no related allowance	126
Average recorded investment - with no related allowance	133
Interest income recognized - with no related allowance	3
Unpaid principal balance	126
Related allowance
Impaired Loans	124
Average recorded investment	133
Interest income recognized	3
Residential Portfolio Segment [Member] | Real Estate Sector [Member] | Acquired Loans [Member]
Recorded investment - with no related allowance	1,268	1,300
Unpaid principal balance - with no related allowance	1,268	1,300
Average recorded investment - with no related allowance	1,284	1,320
Interest income recognized - with no related allowance	49	68
Unpaid principal balance	1,268	1,300
Related allowance
Impaired Loans	1,268	1,300
Average recorded investment	1,284	1,320
Interest income recognized	49	68
Commercial Portfolio Segment [Member] | Real Estate Sector [Member]
Recorded investment - with no related allowance	2,830	2,772
Unpaid principal balance - with no related allowance	2,830	2,772
Average recorded investment - with no related allowance	2,947	2,991
Interest income recognized - with no related allowance	105	147
Unpaid principal balance	4,325	4,458
Recorded investment - with related allowance	1,495	1,596
Related allowance	392	474
Unpaid principal balance - with related allowance	1,495	1,686
Average recorded investment - with related allowance	1,516	1,644
Interest income recognized - with related allowance	49	66
Impaired Loans	4,325	4,368
Average recorded investment	4,463	4,635
Interest income recognized	154	213
Commercial Portfolio Segment [Member] | Real Estate Sector [Member] | Originated Loans [Member]
Recorded investment - with no related allowance	1,886	2,112
Unpaid principal balance - with no related allowance	1,886	2,112
Average recorded investment - with no related allowance	1,972	2,228
Interest income recognized - with no related allowance	67	100
Unpaid principal balance	3,381	3,361
Recorded investment - with related allowance	1,495	1,249
Related allowance	392	360
Unpaid principal balance - with related allowance	1,495	1,249
Average recorded investment - with related allowance	1,516	1,277
Interest income recognized - with related allowance	49	66
Impaired Loans	3,381	3,361
Average recorded investment	3,488	3,505
Interest income recognized	116	166
Commercial Portfolio Segment [Member] | Real Estate Sector [Member] | Acquired Loans [Member]
Recorded investment - with no related allowance	944	660
Unpaid principal balance - with no related allowance	944	660
Average recorded investment - with no related allowance	975	763
Interest income recognized - with no related allowance	38	47
Unpaid principal balance	944	1,097
Recorded investment - with related allowance		347
Related allowance		114
Unpaid principal balance - with related allowance		437
Average recorded investment - with related allowance		367
Interest income recognized - with related allowance
Impaired Loans	944	1,007
Average recorded investment	975	1,130
Interest income recognized	38	47
Commercial Portfolio Segment [Member] | Commercial and Industrial Sector [Member]
Recorded investment - with no related allowance	1,014	1,266
Unpaid principal balance - with no related allowance	1,014	1,266
Average recorded investment - with no related allowance	1,098	1,434
Interest income recognized - with no related allowance	39	66
Unpaid principal balance	2,902	3,333
Recorded investment - with related allowance	1,814	2,061
Related allowance	646	686
Unpaid principal balance - with related allowance	1,888	2,067
Average recorded investment - with related allowance	2,128	2,092
Interest income recognized - with related allowance	79	33
Impaired Loans	2,828	3,327
Average recorded investment	3,226	3,526
Interest income recognized	118	99
Commercial Portfolio Segment [Member] | Commercial and Industrial Sector [Member] | Originated Loans [Member]
Recorded investment - with no related allowance	751	825
Unpaid principal balance - with no related allowance	751	825
Average recorded investment - with no related allowance	747	891
Interest income recognized - with no related allowance	28	45
Unpaid principal balance	2,555	2,771
Recorded investment - with related allowance	1,730	1,940
Related allowance	636	655
Unpaid principal balance - with related allowance	1,804	1,946
Average recorded investment - with related allowance	2,025	1,951
Interest income recognized - with related allowance	75	27
Impaired Loans	2,481	2,765
Average recorded investment	2,772	2,842
Interest income recognized	103	72
Commercial Portfolio Segment [Member] | Commercial and Industrial Sector [Member] | Acquired Loans [Member]
Recorded investment - with no related allowance	263	441
Unpaid principal balance - with no related allowance	263	441
Average recorded investment - with no related allowance	351	543
Interest income recognized - with no related allowance	11	21
Unpaid principal balance	347	562
Recorded investment - with related allowance	84	121
Related allowance	10	31
Unpaid principal balance - with related allowance	84	121
Average recorded investment - with related allowance	103	141
Interest income recognized - with related allowance	4	6
Impaired Loans	347	562
Average recorded investment	454	684
Interest income recognized	15	27
Construction Portfolio Segment [Member] | Real Estate Sector [Member]
Recorded investment - with no related allowance	609	702
Unpaid principal balance - with no related allowance	609	702
Average recorded investment - with no related allowance	640	843
Interest income recognized - with no related allowance	20	28
Unpaid principal balance	609	702
Related allowance
Impaired Loans	609	702
Average recorded investment	640	843
Interest income recognized	20	28
Construction Portfolio Segment [Member] | Real Estate Sector [Member] | Originated Loans [Member]
Recorded investment - with no related allowance	609	702
Unpaid principal balance - with no related allowance	609	702
Average recorded investment - with no related allowance	640	843
Interest income recognized - with no related allowance	20	28
Unpaid principal balance	609	702
Related allowance
Impaired Loans	609	702
Average recorded investment	640	843
Interest income recognized	20	28
Other Portfolio Segment [Member]
Recorded investment - with no related allowance	2	4
Unpaid principal balance - with no related allowance	2	4
Average recorded investment - with no related allowance	3	6
Interest income recognized - with no related allowance		1
Unpaid principal balance	2	4
Related allowance
Impaired Loans	2	4
Average recorded investment	3	6
Interest income recognized		1
Other Portfolio Segment [Member] | Originated Loans [Member]
Recorded investment - with no related allowance	2	4
Unpaid principal balance - with no related allowance	2	4
Average recorded investment - with no related allowance	3	6
Interest income recognized - with no related allowance		1
Unpaid principal balance	2	4
Related allowance
Impaired Loans	2	4
Average recorded investment	3	6
Interest income recognized		$ 1