Note 3 - Loans Receivable and Related Allowance for Loan Losses - Impaired Loans by Class (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Impaired loans with specific allowance, unpaid principal balance	$ 458	$ 76
Impaired loans with specific allowance, recorded investment	458	76
Related allowance	60	5
Impaired loans with specific allowance, average recorded investment	204	77
Impaired loans with specific allowance, interest income recognized in period	22	3
Impaired loans with specific allowance, cash basis interest recognized in period	15	3
Impaired loans with no specific allowance, unpaid principal balance	1,767	519
Impaired loans with no specific allowance, recorded investment	1,656	407
Impaired loans with no specific allowance, average recorded investment	1,549	1,399
Impaired loans with no specific allowance, interest income recognized in period	93	99
Impaired loans with no specific allowance, cash basis interest recognized in period	79	41
Residential Portfolio Segment [Member]
Impaired loans with specific allowance, unpaid principal balance		72
Impaired loans with specific allowance, recorded investment		72
Related allowance		5
Impaired loans with specific allowance, average recorded investment	43	72
Impaired loans with specific allowance, interest income recognized in period		3
Impaired loans with specific allowance, cash basis interest recognized in period		3
Impaired loans with no specific allowance, unpaid principal balance	440	398
Impaired loans with no specific allowance, recorded investment	329	286
Impaired loans with no specific allowance, average recorded investment	300	301
Impaired loans with no specific allowance, interest income recognized in period	7	4
Impaired loans with no specific allowance, cash basis interest recognized in period	7	4
Home Equity Loans and Lines of Credit [Member]
Impaired loans with specific allowance, unpaid principal balance		4
Impaired loans with specific allowance, recorded investment		4
Related allowance
Impaired loans with specific allowance, average recorded investment	2	5
Impaired loans with specific allowance, interest income recognized in period
Impaired loans with specific allowance, cash basis interest recognized in period
Impaired loans with no specific allowance, unpaid principal balance	3
Impaired loans with no specific allowance, recorded investment	3
Impaired loans with no specific allowance, average recorded investment	2
Impaired loans with no specific allowance, interest income recognized in period
Impaired loans with no specific allowance, cash basis interest recognized in period
Commercial Real Estate Portfolio Segment [Member]
Impaired loans with specific allowance, unpaid principal balance	380
Impaired loans with specific allowance, recorded investment	380
Related allowance	40
Impaired loans with specific allowance, average recorded investment	106
Impaired loans with specific allowance, interest income recognized in period	17
Impaired loans with specific allowance, cash basis interest recognized in period	11
Impaired loans with no specific allowance, unpaid principal balance	1,259	81
Impaired loans with no specific allowance, recorded investment	1,259	81
Impaired loans with no specific allowance, average recorded investment	1,167	1,019
Impaired loans with no specific allowance, interest income recognized in period	76	88
Impaired loans with no specific allowance, cash basis interest recognized in period	66	35
Commercial Portfolio Segment [Member]
Impaired loans with specific allowance, unpaid principal balance	78
Impaired loans with specific allowance, recorded investment	78
Related allowance	20
Impaired loans with specific allowance, average recorded investment	53
Impaired loans with specific allowance, interest income recognized in period	5
Impaired loans with specific allowance, cash basis interest recognized in period	4
Impaired loans with no specific allowance, unpaid principal balance	65	40
Impaired loans with no specific allowance, recorded investment	65	40
Impaired loans with no specific allowance, average recorded investment	80	79
Impaired loans with no specific allowance, interest income recognized in period	10	7
Impaired loans with no specific allowance, cash basis interest recognized in period	6	2
Consumer Portfolio Segment [Member]
Impaired loans with specific allowance, unpaid principal balance
Impaired loans with specific allowance, recorded investment
Related allowance
Impaired loans with specific allowance, average recorded investment
Impaired loans with specific allowance, interest income recognized in period
Impaired loans with specific allowance, cash basis interest recognized in period
Impaired loans with no specific allowance, unpaid principal balance
Impaired loans with no specific allowance, recorded investment
Impaired loans with no specific allowance, average recorded investment
Impaired loans with no specific allowance, interest income recognized in period
Impaired loans with no specific allowance, cash basis interest recognized in period

Amount of allowance for credit losses related to recorded investment.

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Data Type:	xbrli:monetaryItemType
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- Definition

Amount of average investment of impaired financing receivables for which there is no 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 17
-URI http://asc.fasb.org/extlink&oid=121611835&loc=d3e5258-111524

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-Publisher FASB
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-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=121611835&loc=d3e5212-111524

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- Definition

Amount of interest income, recognized on accrual basis, on financing receivables that are recognized as impaired, for which there is no related allowance for credit losses.

+ References

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- Definition

Amount of interest income, recognized on cash basis, on financing receivables, for which there is no related allowance for credit losses and are recognized as impaired.

+ References

+ Details

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- Definition

Amount of investment in impaired financing receivables for which there is no 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=121611835&loc=SL6953550-111524

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- Definition

Amount of unpaid principal balance of impaired financing receivables for which there is no related allowance for credit losses.

+ References

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- Definition

Amount of average investment of 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 15
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=121611835&loc=d3e5212-111524

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-Publisher FASB
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-SubTopic 10
-Section 50
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=121611835&loc=d3e5258-111524

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- Definition

Amount of interest income, recognized on accrual basis, on financing receivables, for which there is a related allowance for credit losses and are recognized as impaired.

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Amount of interest income on financing receivables, for which there is a related allowance for credit losses, recognized on a cash-basis method of accounting that the financing receivables were impaired.

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

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Unpaid principal balance of impaired financing receivables for which there is a related allowance for credit losses.

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