Note 5 - Allowances for Loan Losses (Details Textual)	12 Months Ended
Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Impaired Financing Receivable, Average Recorded Investment, Total	$ 18,105,000	$ 22,801,000	$ 25,387,000
Impaired Financing Receivable, Interest Income, Accrual Method, Total	386,000	451,000	607,000
Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans	$ 548,000	$ 498,000	590,000
Financing Receivable, Modifications, Number of Contracts	0	0
Financing Receivable, Troubled Debt Restructuring, Subsequent Default, Number of Contracts	0	3
Number of Mortgage Loans in Process of Foreclosure	1	0
Real Estate Acquired Through Foreclosure	$ 1,730,000	$ 6,223,000
Residential Portfolio Segment [Member]
Impaired Financing Receivable, Average Recorded Investment, Total	461,000		$ 26,000
Real Estate Acquired Through Foreclosure	$ 0	$ 0

Number of mortgage loans in process of foreclosure.

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

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953676-111524

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Number of financing receivable contracts modified as troubled debt restructuring within previous 12 months, with subsequent payment default.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953682-111524

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

+ References

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-Publisher FASB
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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

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Reflects the amount of additional interest income that would have been recorded if impaired or nonperforming loans were instead current, in compliance with their original terms, and outstanding throughout the reporting period or since origination (if held for part of the period).

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- Definition

Carrying amount as of the balance sheet date of land and buildings obtained through foreclosure proceedings or defeasance in full or partial satisfaction of a debt arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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