Note 9 - Allowance for Loan Losses and Credit Quality Information - Non-accrual Loans (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Non-accrual loans	$ 3,016	$ 3,144
Residential Portfolio Segment [Member]
Non-accrual loans	960	949
Commercial Real Estate Portfolio Segment [Member] | Real Estate Loan [Member]
Non-accrual loans	34	35
Commercial Real Estate Portfolio Segment [Member] | Commercial Real Estate Other [Member]
Non-accrual loans	1,398	1,329
Consumer Portfolio Segment [Member]
Non-accrual loans	551	553
Commercial Portfolio Segment [Member]
Non-accrual loans	$ 73	$ 278