Note 5 - Loans and Allowance for Loan Losses (Details Textual)	12 Months Ended
Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Unamortized Loan Commitment and Origination Fees and Unamortized Discounts or Premiums	$ 1,041,000	$ 837,000
Loans and Leases Receivable, Gross	414,617,000	385,764,000
Off-balance-sheet Commitments to Related Parties	$ 2,800,000	$ 2,400,000
Financing Receivable, Allowance for Credit Losses, Loss Factor Increase	0.33%
Financing Receivable, Allowance for Credit Losses, Loss Factor	20.00%
Financing Receivable, Allowance for Credit Losses Risk Factor	1.18	1.18
Impaired Financing Receivable, Interest Income, Cash Basis Method	$ 0	$ 0	$ 0
Loans and Leases Receivable, Impaired, Commitment to Lend	0	$ 0
Financing Receivable, Modifications, Number of Contracts		0	0
Troubled Debt Restructuring, Principal Charge-offs	$ 0	$ 0	$ 0
Financing Receivable, Modifications, Subsequent Default, Number of Contracts	0	0	2
Financing Receivable, Modifications, Subsequent Default, Recorded Investment			$ 187,000
Financial Receivable, Trouble Debt Restructure, Defaulted, Provisions Loan Losses or Net Charge-offs	$ 0	$ 0	0
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance	625,000	754,000
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Allowance for Loan Losses	2,000	0
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Provision for Loan Losses	2,000
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Allowance for Loan Losses, Decreases		0	$ 0
Qualitative Factor Past Due Loans [Member]
Financing Receivable, Allowance for Credit Losses, Effect of Change in Method	$ 2,100,000	$ 1,800,000
Financing Receivable, Allowance for Credit Losses Risk Factor	1.2	1.2
Qualitative Factor Economic Condition [Member]
Financing Receivable, Allowance for Credit Losses Risk Factor	1.2	1.2
Qualitative Factor Other Internal and External Factors [Member]
Financing Receivable, Allowance for Credit Losses Risk Factor	1.3	1.3
Overall Qualitative Factor [Member]
Financing Receivable, Allowance for Credit Losses Risk Factor	1.18	1.18
Allowance for Loan and Lease Losses, Period Increase (Decrease)	$ 536,000	$ 501,000
Residential Mortgage Segment [Member]
Loans and Leases Receivable, Gross	3,200,000	3,700,000
Amount of Loans Serviced for Others	117,000	126,000
Classified Loans [Member]
Allowance for Loan and Lease Losses, Period Increase (Decrease)	$ 506,000	$ 559,000
Real Estate Mortgage Portfolio Segment [Member] \| Residential Loan [Member]
Loan to Value Ratio	90.00%	90.00%
Loans and Leases Receivable, Gross	$ 136,960,000	$ 138,377,000
Financing Receivable, Modifications, Number of Contracts	1
Financing Receivable, Modifications, Pre-Modification Recorded Investment	$ 65,000
Financing Receivable, Modifications, Post-Modification Recorded Investment	65,000
Peoples Bancorp, Inc [Member]
Unamortized Loan Commitment and Origination Fees and Unamortized Discounts or Premiums	$ 87,000	$ 137,000

The amount of mortgage loans serviced for the benefit of others.

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The amount of provisions loan losses or net charge-offs recognized as a result of defaulted TDRs during the period.

+ References

No definition available.

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- Definition

Percentage of loss factor related to financing receivables.

+ References

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Percentage of increase during the period in of loss factors related to financing receivables.

+ References

No definition available.

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Represents financing receivable allowance for credit losses risk factor.

+ References

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Ratio of the appraised value of a property to its mortgage.

+ References

No definition available.

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- Definition

Amount of off-balance-sheet commitments (including commitments to make loans, unused lines of credit and letters of credit) to related parties.

+ References

No definition available.

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Represents the amount of principal charge-offs for troubled debt restructuring.

+ References

No definition available.

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Amount of increase (decrease) of allowance reserve for credit loss.

+ References

Reference 1: 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

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Reserve for loans impairments recorded after acquisition as a result of current information and events which result in it being probable that estimated cash flows will be less than previously expected or because actual cash flows are less than cash flows previously expected. This relates to loans not accounted for as debt securities, with evidence of deterioration of credit quality since origination that was acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=82894903&loc=d3e15032-111544

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Amount of reduction in the reserve for loans impairments as a result of current information and events which result in it being probable that estimated cash flows will be significantly higher than previously expected or because actual cash flows are significantly greater than cash flows previously expected for loans not accounted for as debt securities, with evidence of deterioration of credit quality since origination that was acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

+ References

No definition available.

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- Definition

The undiscounted sum of all amounts, including amounts deemed principal, interest, fees, penalties, and other under the loan, owed to the investor at the reporting date, whether or not currently due and whether or not any such amounts have been written or charged off by the investor. This relates to loans not accounted for as debt securities, with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 15
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82894507&loc=d3e13503-111538

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- Definition

Amount of expense related to loan loss not accounted for as debt securities, with evidence of deterioration of credit quality.

+ References

No definition available.

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- Definition

The effect of a change in method or methods for calculating the allowance for credit losses on the current period provision.

+ 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 (d)
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- Definition

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

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-Publisher FASB
-Name Accounting Standards Codification
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Post-modification amount of investment in financing receivables modified by troubled debt restructurings.

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

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- Definition

Number of financing receivables that have been modified by troubled debt restructurings within the previous 12 months and for which there was a payment default.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Amount of investment related to financing receivables modified by troubled debt restructurings within the previous 12 months, for which there was a payment default.

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- Definition

Amount of interest income recognized on a cash-basis method of accounting 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
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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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Reflects the unfunded portion of contractual agreements to lend funds to borrowers for loans whose terms have been modified by troubled debt restructuring.

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Amount of deferred fees paid by borrowers and unamortized costs incurred to originate loans and leases, unamortized loan commitments and loan syndication fees, and premiums over or discounts from face amounts of loans that are being amortized into income as an adjustment to yield. Excludes amounts for loans and leases covered under loss sharing agreements.

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