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Note 4 - Loans and Related Allowance for Loan and Lease Losses - Additional Information on Impaired Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Average recorded investment	$ 12,836	$ 13,411	$ 13,440
Interest income recognized	715	509	725
Commercial And Industrial [Member]
Average recorded investment	2,378	1,211	1,468
Interest income recognized	178	32	100
Real Estate Construction Porfolio Segment [Member]
Average recorded investment	565	1,281	2,407
Interest income recognized	1	10	115
Real Estate Mortgage Portfolio Segment [Member] | Residential Loan [Member]
Average recorded investment	3,068	3,529	4,356
Interest income recognized	89	98	160
Real Estate Mortgage Portfolio Segment [Member] | Commercial Loans [Member]
Average recorded investment	6,820	7,384	5,203
Interest income recognized	446	368	350
Consumer Portfolio Segment [Member]
Average recorded investment	5	6	6
Interest income recognized	$ 1	$ 1

X

- Definition

Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5212-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5258-111524

+ Details

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Namespace Prefix:	us-gaap_
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Balance Type:	debit
Period Type:	duration

X

- Definition

Amount of interest income recognized that the financing receivables (with related allowance for credit losses and without a related allowance for credit losses) were impaired.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5212-111524

+ Details

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- Details

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- Details

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