Note 6 - Allowance for Loan Losses and Credit Quality Information - Troubled Debt Restructurings Subsequently Defaulted (Details) $ in Thousands	12 Months Ended
Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Number of Contracts that subsequently defaulted	1	2
Outstanding Recorded Investment	$ 65	$ 187
Commercial Real Estate Portfolio Segment [Member] \| Commercial Real Estate Other [Member]
Number of Contracts that subsequently defaulted	0	1
Outstanding Recorded Investment	$ 0	$ 183
Consumer Portfolio Segment [Member]
Number of Contracts that subsequently defaulted	1	1
Outstanding Recorded Investment	$ 65	$ 4

Amount of investment related to financing receivables modified by troubled debt restructurings within the previous 12 months, for which there was a payment default.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953682-111524

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration