Note 9 - Allowance for Loan Losses and Credit Quality Information - Troubled Debt Restructurings (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Troubled debt restructurings	$ 2,423	$ 2,476
Performing Financial Instruments [Member]
Troubled debt restructurings	968	1,018
Nonperforming Financial Instruments [Member]
Troubled debt restructurings	1,455	1,458
Residential Portfolio Segment [Member]
Troubled debt restructurings	654	636
Residential Portfolio Segment [Member] | Performing Financial Instruments [Member]
Troubled debt restructurings	496	496
Residential Portfolio Segment [Member] | Nonperforming Financial Instruments [Member]
Troubled debt restructurings	158	140
Commercial Real Estate Portfolio Segment [Member]
Troubled debt restructurings	1,077	1,110
Commercial Real Estate Portfolio Segment [Member] | Performing Financial Instruments [Member]
Troubled debt restructurings	0	0
Commercial Real Estate Portfolio Segment [Member] | Nonperforming Financial Instruments [Member]
Troubled debt restructurings	1,077	1,110
Consumer Portfolio Segment [Member]
Troubled debt restructurings	508	522
Consumer Portfolio Segment [Member] | Performing Financial Instruments [Member]
Troubled debt restructurings	337	367
Consumer Portfolio Segment [Member] | Nonperforming Financial Instruments [Member]
Troubled debt restructurings	171	155
Commercial Portfolio Segment [Member]
Troubled debt restructurings	184	208
Commercial Portfolio Segment [Member] | Performing Financial Instruments [Member]
Troubled debt restructurings	135	155
Commercial Portfolio Segment [Member] | Nonperforming Financial Instruments [Member]
Troubled debt restructurings	$ 49	$ 53