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Note 5 - Allowance for Loan Losses, Nonperforming Assets and Impaired Loans - Restructurings By Class (Details) $ in Thousands		12 Months Ended
		Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014
Number of contracts		10	4	6
Pre-modification outstanding principal balance		$ 1,387	$ 3,042	$ 3,628
Post-modification outstanding principal balance	[1]	$ 1,387	$ 3,043	$ 3,541
Consumer Real Estate Portfolio Segment [Member] | Closed End First Liens [Member]
Number of contracts		1
Pre-modification outstanding principal balance		$ 8
Post-modification outstanding principal balance	[1]	$ 8
Commercial Real Estate Portfolio Segment [Member]
Number of contracts					2
Commercial Real Estate Portfolio Segment [Member] | Commercial Real Estate Other [Member]
Number of contracts		1	2
Pre-modification outstanding principal balance		$ 132	$ 3,008
Post-modification outstanding principal balance	[1]	$ 132	$ 3,008
Commercial Real Estate Portfolio Segment [Member] | Commercial Real Estate, Owner Occupied [Member]
Number of contracts				3
Pre-modification outstanding principal balance				$ 2,710
Post-modification outstanding principal balance	[1]			$ 2,623
Real Estate Construction Portfolio Segment[Member] | Construction, 1-4 Family Residential [Member]
Number of contracts				2
Pre-modification outstanding principal balance				$ 718
Post-modification outstanding principal balance	[1]			$ 718
Commercial Non Real Estate Segment [Member]
Number of contracts			1
Commercial Non Real Estate Segment [Member] | Commercial and Industrial [Member]
Number of contracts		4	1	1
Pre-modification outstanding principal balance		$ 1,221	$ 29	$ 200
Post-modification outstanding principal balance	[1]	$ 1,221	$ 30	$ 200
Consumer Non Real Estate Portfolio Segment [Member] | Automobile Loan [Member]
Number of contracts		4	1
Pre-modification outstanding principal balance		$ 26	$ 5
Post-modification outstanding principal balance	[1]	$ 26	$ 5
[1] Post-modification outstanding recorded investment considers amounts immediately following the modification. Amounts do not reflect balances at the end of the period.

X

- Definition

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

+ References

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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- Definition

Post-modification amount of investment in financing receivables modified by troubled debt restructurings.

+ References

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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- Definition

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+ References

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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