Note 8 - Non-accrual Loans (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Financing Receivable Recorded Investment Past Due [Line Items]
Loans receivable	$ 0	$ 0
Loans receivable	10,001	11,704
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Loans receivable	0	0
Loans receivable	4,888	5,901
Commercial Portfolio Segment [Member] | Construction Loans [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Loans receivable	0	0
Loans receivable	0	0
Commercial Portfolio Segment [Member] | Secured by Commercial Real Estate [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Loans receivable	0	0
Loans receivable	2,998	3,640
Commercial Portfolio Segment [Member] | Secured by Residential Real Estate [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Loans receivable	0	0
Loans receivable	747	851
State and Political Subdivisions Portfolio Segment [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Loans receivable	0	0
Loans receivable	0	0
Retail Portfolio Segment [Member] | Consumer Loans [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Loans receivable	0	0
Loans receivable	148	139
Retail Portfolio Segment [Member] | Family Residential Mortgages [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Loans receivable	0	0
Loans receivable	495	636
Retail Portfolio Segment [Member] | Home Equity Loans and Lines [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Loans receivable	0	0
Loans receivable	$ 725	$ 537