Note 15 - Assets and Liabilities Measured and Reported at Fair Value (Details Textual) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Impaired Financing Receivable, Related Allowance	$ 1,470	$ 48
Impaired Financing Receivable, with Related Allowance, Recorded Investment	5,760	48
Other Real Estate, Foreclosed Assets, and Repossessed Assets, Total	360	2,600
Impaired Loans [Member] \| Appraisal Discount Method [Member]
Assets, Fair Value Disclosure	5,900	2,600
Impaired Financing Receivable, Related Allowance	1,500	48
Impaired Financing Receivable, with Related Allowance, Recorded Investment	7,400	2,600
Mortgage Servicing Rights [Member]
Impaired Financing Receivable, Related Allowance	0	0
Fair Value, Measurements, Recurring [Member]
Assets, Fair Value Disclosure	600,068	575,103
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Recurring [Member]
Assets, Fair Value Disclosure	0	0
Financial and Nonfinancial Liabilities, Fair Value Disclosure	$ 0	$ 0

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

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Amount of allowance for credit losses related to recorded investment.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5212-111524

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Amount of investment in impaired financing receivables for which there is a related allowance for credit losses.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 14A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953550-111524

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Fair value of financial and nonfinancial obligations.

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Carrying amount as of the balance sheet date of other real estate and foreclosed assets. Other real estate may include real estate investments, real estate loans that qualify as investments in real estate, and premises that are no longer used in operations may also be included in real estate owned. Foreclosed assets include all assets obtained in full or partial satisfaction of a debt arrangement through foreclosure proceedings.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.10(4))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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