Note 5 - Allowance for Loan Losses (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for loan losses, beginning of period	$ 7,394	$ 7,554	$ 8,001
Provision for (credit to) loan losses	1,400	30	200
Charge-offs	(1,075)	(404)	(787)
Recoveries	122	214	140
Allowance for loan losses, end of period	7,841	7,394	7,554
Commercial Portfolio Segment [Member] \| Commercial and Industrial [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for loan losses, beginning of period	1,459	1,521	1,892
Provision for (credit to) loan losses	2,178	41	(353)
Charge-offs	(960)	(140)	(56)
Recoveries	34	37	38
Allowance for loan losses, end of period	2,711	1,459	1,521
Commercial Portfolio Segment [Member] \| Construction Loans [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for loan losses, beginning of period	449	286	297
Provision for (credit to) loan losses	114	163	(11)
Charge-offs	0	0	0
Recoveries	0	0	0
Allowance for loan losses, end of period	563	449	286
Commercial Portfolio Segment [Member] \| Secured by Commercial Real Estate [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for loan losses, beginning of period	2,646	2,411	2,700
Provision for (credit to) loan losses	(244)	227	(214)
Charge-offs	0	0	(84)
Recoveries	8	8	9
Allowance for loan losses, end of period	2,410	2,646	2,411
Commercial Portfolio Segment [Member] \| Secured by Residential Real Estate [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for loan losses, beginning of period	1,760	1,812	1,630
Provision for (credit to) loan losses	(959)	(44)	687
Charge-offs	(23)	(120)	(531)
Recoveries	38	112	26
Allowance for loan losses, end of period	816	1,760	1,812
State and Political Subdivisions Portfolio Segment [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for loan losses, beginning of period	123	222	221
Provision for (credit to) loan losses	(9)	(99)	1
Charge-offs	0	0	0
Recoveries	0	0	0
Allowance for loan losses, end of period	114	123	222
Retail Portfolio Segment [Member] \| Consumer Loans [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for loan losses, beginning of period	76	76	85
Provision for (credit to) loan losses	41	60	57
Charge-offs	(92)	(92)	(95)
Recoveries	32	32	29
Allowance for loan losses, end of period	57	76	76
Retail Portfolio Segment [Member] \| Family Residential Mortgages [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for loan losses, beginning of period	366	350	312
Provision for (credit to) loan losses	78	16	38
Charge-offs	0	0	0
Recoveries	0	0	0
Allowance for loan losses, end of period	444	366	350
Retail Portfolio Segment [Member] \| Home Equity Loans and Lines [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for loan losses, beginning of period	353	428	453
Provision for (credit to) loan losses	(6)	(91)	(47)
Charge-offs	0	0	0
Recoveries	10	16	22
Allowance for loan losses, end of period	357	353	428
Unallocated Financing Receivables [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for loan losses, beginning of period	162	284	318
Provision for (credit to) loan losses	207	(122)	(34)
Charge-offs	0	0	0
Recoveries	0	0	0
Allowance for loan losses, end of period	369	162	284
Finance Leases Portfolio Segment [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for loan losses, beginning of period	$ 0	164	93
Provision for (credit to) loan losses		(121)	76
Charge-offs		(52)	(21)
Recoveries		9	16
Allowance for loan losses, end of period		$ 0	$ 164

Provision for (credit to) loan and lease losses.

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- Definition

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-Topic 310
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-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(d))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=82894903&loc=d3e15032-111544

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