Note 4 - Loans Receivable and Related Allowance for Loan Losses - Impaired Loans by Class (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Impaired loans with specific allowance, unpaid principal balance	$ 514	$ 506	$ 877
Impaired loans with specific allowance, recorded investment	514	506	877
Related allowance	128	40	285
Impaired loans with specific allowance, average recorded investment	695	482	494
Impaired loans with specific allowance, interest income recognized in period	6	6	41
Impaired loans with specific allowance, cash basis interest recognized in period	6	6	41
Impaired loans with no specific allowance, unpaid principal balance	2,578	1,542	1,121
Impaired loans with no specific allowance, recorded investment	2,467	1,414	1,009
Impaired loans with no specific allowance, average recorded investment	1,738	1,536	1,374
Impaired loans with no specific allowance, interest income recognized in period	36	14	79
Impaired loans with no specific allowance, cash basis interest recognized in period	14	14	79
Residential Portfolio Segment [Member]
Impaired loans with specific allowance, unpaid principal balance	68	69	68
Impaired loans with specific allowance, recorded investment	68	69	68
Related allowance	7	1	1
Impaired loans with specific allowance, average recorded investment	68	35	28
Impaired loans with specific allowance, interest income recognized in period	0	1	3
Impaired loans with specific allowance, cash basis interest recognized in period	0	1	3
Impaired loans with no specific allowance, unpaid principal balance	330	363	338
Impaired loans with no specific allowance, recorded investment	219	251	226
Impaired loans with no specific allowance, average recorded investment	223	290	284
Impaired loans with no specific allowance, interest income recognized in period	1	1	3
Impaired loans with no specific allowance, cash basis interest recognized in period	1	1	3
Home Equity Loans and Lines of Credit [Member]
Impaired loans with specific allowance, unpaid principal balance	0	0	0
Impaired loans with specific allowance, recorded investment	0	0	0
Related allowance	0	0	0
Impaired loans with specific allowance, average recorded investment	0	0	0
Impaired loans with specific allowance, interest income recognized in period	0	0	0
Impaired loans with specific allowance, cash basis interest recognized in period	0	0	0
Impaired loans with no specific allowance, unpaid principal balance	4	4	4
Impaired loans with no specific allowance, recorded investment	4	4	4
Impaired loans with no specific allowance, average recorded investment	4	4	4
Impaired loans with no specific allowance, interest income recognized in period	0	0	0
Impaired loans with no specific allowance, cash basis interest recognized in period	0	0	0
Commercial Real Estate Portfolio Segment [Member]
Impaired loans with specific allowance, unpaid principal balance	443	373	559
Impaired loans with specific allowance, recorded investment	443	373	559
Related allowance	118	33	88
Impaired loans with specific allowance, average recorded investment	501	376	387
Impaired loans with specific allowance, interest income recognized in period	6	4	30
Impaired loans with specific allowance, cash basis interest recognized in period	6	4	30
Impaired loans with no specific allowance, unpaid principal balance	2,158	1,110	666
Impaired loans with no specific allowance, recorded investment	2,158	1,094	666
Impaired loans with no specific allowance, average recorded investment	1,412	1,177	990
Impaired loans with no specific allowance, interest income recognized in period	31	12	71
Impaired loans with no specific allowance, cash basis interest recognized in period	9	12	71
Commercial Portfolio Segment [Member]
Impaired loans with specific allowance, unpaid principal balance	3	64	250
Impaired loans with specific allowance, recorded investment	3	64	250
Related allowance	3	6	196
Impaired loans with specific allowance, average recorded investment	126	71	79
Impaired loans with specific allowance, interest income recognized in period	0	1	8
Impaired loans with specific allowance, cash basis interest recognized in period	0	1	8
Impaired loans with no specific allowance, unpaid principal balance	86	65	113
Impaired loans with no specific allowance, recorded investment	86	65	113
Impaired loans with no specific allowance, average recorded investment	99	65	96
Impaired loans with no specific allowance, interest income recognized in period	4	1	5
Impaired loans with no specific allowance, cash basis interest recognized in period	4	1	5
Consumer Portfolio Segment [Member]
Impaired loans with specific allowance, unpaid principal balance	0	0	0
Impaired loans with specific allowance, recorded investment	0	0	0
Related allowance	0	0	0
Impaired loans with specific allowance, average recorded investment	0	0	0
Impaired loans with specific allowance, interest income recognized in period	0	0	0
Impaired loans with specific allowance, cash basis interest recognized in period	0	0	0
Impaired loans with no specific allowance, unpaid principal balance	0	0	0
Impaired loans with no specific allowance, recorded investment	0	0	0
Impaired loans with no specific allowance, average recorded investment	0	0	0
Impaired loans with no specific allowance, interest income recognized in period	0	0	0
Impaired loans with no specific allowance, cash basis interest recognized in period	$ 0	$ 0	$ 0

Amount of allowance for credit losses related to recorded investment.

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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 https://asc.fasb.org/extlink&oid=123577603&loc=d3e5258-111524

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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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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

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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 https://asc.fasb.org/extlink&oid=123577603&loc=SL6953550-111524

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

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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 https://asc.fasb.org/extlink&oid=123577603&loc=d3e5212-111524

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-Publisher FASB
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-SubTopic 10
-Section 50
-Paragraph 17
-URI https://asc.fasb.org/extlink&oid=123577603&loc=d3e5258-111524

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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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