Note 9 - Allowance for Loan Losses and Credit Quality Information - Non-accrual Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Non-accrual loans	$ 2,522	$ 2,678
Residential Portfolio Segment [Member]
Non-accrual loans	751	730
Commercial Real Estate Portfolio Segment [Member] | Real Estate Loan [Member]
Non-accrual loans	199	201
Commercial Real Estate Portfolio Segment [Member] | Commercial Real Estate Other [Member]
Non-accrual loans	1,077	1,110
Consumer Portfolio Segment [Member]
Non-accrual loans	283	489
Commercial Portfolio Segment [Member]
Non-accrual loans	$ 212	$ 148