Note 5 - Internal Risk Ratings and Payment Activity (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	$ 733,078	$ 632,999
Excluding Retail Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	595,004	508,680
Pass [Member] | Excluding Retail Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	566,703	480,374
Special Mention [Member] | Excluding Retail Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	11,654	6,102
Substandard [Member] | Excluding Retail Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	16,647	22,204
Doubtful [Member] | Excluding Retail Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	0	0
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	147,190	110,233
Commercial Portfolio Segment [Member] | Construction Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	51,157	39,268
Commercial Portfolio Segment [Member] | Secured by Commercial Real Estate [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	286,867	255,188
Commercial Portfolio Segment [Member] | Secured by Residential Real Estate [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	71,703	68,731
Commercial Portfolio Segment [Member] | Pass [Member] | Commercial and Industrial [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	139,820	102,396
Commercial Portfolio Segment [Member] | Pass [Member] | Construction Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	51,156	39,259
Commercial Portfolio Segment [Member] | Pass [Member] | Secured by Commercial Real Estate [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	268,069	238,290
Commercial Portfolio Segment [Member] | Pass [Member] | Secured by Residential Real Estate [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	69,571	65,169
Commercial Portfolio Segment [Member] | Special Mention [Member] | Commercial and Industrial [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	863	686
Commercial Portfolio Segment [Member] | Special Mention [Member] | Construction Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	0	0
Commercial Portfolio Segment [Member] | Special Mention [Member] | Secured by Commercial Real Estate [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	10,569	5,185
Commercial Portfolio Segment [Member] | Special Mention [Member] | Secured by Residential Real Estate [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	222	231
Commercial Portfolio Segment [Member] | Substandard [Member] | Commercial and Industrial [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	6,507	7,151
Commercial Portfolio Segment [Member] | Substandard [Member] | Construction Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	1	9
Commercial Portfolio Segment [Member] | Substandard [Member] | Secured by Commercial Real Estate [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	8,229	11,713
Commercial Portfolio Segment [Member] | Substandard [Member] | Secured by Residential Real Estate [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	1,910	3,331
Commercial Portfolio Segment [Member] | Doubtful [Member] | Commercial and Industrial [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	0	0
Commercial Portfolio Segment [Member] | Doubtful [Member] | Construction Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	0	0
Commercial Portfolio Segment [Member] | Doubtful [Member] | Secured by Commercial Real Estate [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	0	0
Commercial Portfolio Segment [Member] | Doubtful [Member] | Secured by Residential Real Estate [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	0	0
State and Political Subdivisions Portfolio Segment [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	38,087	35,260
State and Political Subdivisions Portfolio Segment [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	38,087	35,260
State and Political Subdivisions Portfolio Segment [Member] | Special Mention [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	0	0
State and Political Subdivisions Portfolio Segment [Member] | Substandard [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	0	0
State and Political Subdivisions Portfolio Segment [Member] | Doubtful [Member]
Financing Receivable Recorded Investment [Line Items]
Loans and leases receivable	$ 0	$ 0