Note 6 - Allowance for Loan Losses and Credit Quality Information - Financial Effects of Troubled Debt Restructurings (Details) $ in Thousands	12 Months Ended
Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Number of Contracts	19	25
Pre- modification Outstanding Recorded Investment	$ 1,286	$ 2,164
Post- modification Outstanding Recorded Investment	$ 1,221	$ 2,122
Residential Portfolio Segment [Member]
Number of Contracts	3	4
Pre- modification Outstanding Recorded Investment	$ 282	$ 251
Post- modification Outstanding Recorded Investment	$ 514	$ 263
Commercial Real Estate Portfolio Segment [Member] \| Commercial Real Estate Other [Member]
Number of Contracts	0	1
Pre- modification Outstanding Recorded Investment	$ 0	$ 1,274
Post- modification Outstanding Recorded Investment	$ 0	$ 1,274
Consumer Portfolio Segment [Member]
Number of Contracts	15	18
Pre- modification Outstanding Recorded Investment	$ 588	$ 382
Post- modification Outstanding Recorded Investment	$ 591	$ 384
Commercial Portfolio Segment [Member] \| Commercial Business Other [Member]
Number of Contracts	1	2
Pre- modification Outstanding Recorded Investment	$ 416	$ 257
Post- modification Outstanding Recorded Investment	$ 116	$ 201

Number of financing receivables that have been modified by troubled debt restructurings.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953676-111524

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