Note 4 - Loans Receivable and Related Allowance for Loan Losses - Impaired Loans by Class (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended	12 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Impaired loans with specific allowance, unpaid principal balance	$ 319	$ 147	$ 319	$ 147	$ 458
Impaired loans with specific allowance, recorded investment	319	147	319	147	458
Related allowance	31	12	31	12	60
Impaired loans with specific allowance, average recorded investment	412	208	427	164	204
Impaired loans with specific allowance, interest income recognized in period	5	1	8	3	22
Impaired loans with specific allowance, cash basis interest recognized in period	5	1	8	3	15
Impaired loans with no specific allowance, unpaid principal balance	1,561	2,259	1,561	2,259	1,767
Impaired loans with no specific allowance, recorded investment	1,449	2,148	1,449	2,148	1,656
Impaired loans with no specific allowance, average recorded investment	1,432	1,768	1,507	1,314	1,549
Impaired loans with no specific allowance, interest income recognized in period	13	44	29	59	93
Impaired loans with no specific allowance, cash basis interest recognized in period	13	26	29	40	79
Residential Portfolio Segment [Member]
Impaired loans with specific allowance, unpaid principal balance	0	71	0	71	0
Impaired loans with specific allowance, recorded investment	0	71	0	71	0
Related allowance	0	1	0	1	0
Impaired loans with specific allowance, average recorded investment	35	71	23	71	43
Impaired loans with specific allowance, interest income recognized in period	0	1	0	2	0
Impaired loans with specific allowance, cash basis interest recognized in period	0	1	0	2	0
Impaired loans with no specific allowance, unpaid principal balance	424	384	424	384	440
Impaired loans with no specific allowance, recorded investment	312	273	312	273	329
Impaired loans with no specific allowance, average recorded investment	282	276	297	279	300
Impaired loans with no specific allowance, interest income recognized in period	1	0	2	1	7
Impaired loans with no specific allowance, cash basis interest recognized in period	1	0	2	1	7
Home Equity Loans and Lines of Credit [Member]
Impaired loans with specific allowance, unpaid principal balance	0	4	0	4	0
Impaired loans with specific allowance, recorded investment	0	4	0	4	0
Related allowance	0	0	0	0	0
Impaired loans with specific allowance, average recorded investment	0	4	0	4	2
Impaired loans with specific allowance, interest income recognized in period	0	0	0	0	0
Impaired loans with specific allowance, cash basis interest recognized in period	0	0	0	0	0
Impaired loans with no specific allowance, unpaid principal balance	4	0	4	0	3
Impaired loans with no specific allowance, recorded investment	4	0	4	0	3
Impaired loans with no specific allowance, average recorded investment	4	0	4	0	2
Impaired loans with no specific allowance, interest income recognized in period	0	0	0	0	0
Impaired loans with no specific allowance, cash basis interest recognized in period	0	0	0	0	0
Commercial Real Estate Portfolio Segment [Member]
Impaired loans with specific allowance, unpaid principal balance	315	0	315	0	380
Impaired loans with specific allowance, recorded investment	315	0	315	0	380
Related allowance	27	0	27	0	40
Impaired loans with specific allowance, average recorded investment	344	75	356	50	106
Impaired loans with specific allowance, interest income recognized in period	5	0	8	0	17
Impaired loans with specific allowance, cash basis interest recognized in period	5	0	8	0	11
Impaired loans with no specific allowance, unpaid principal balance	1,013	1,734	1,013	1,734	1,259
Impaired loans with no specific allowance, recorded investment	1,013	1,734	1,013	1,734	1,259
Impaired loans with no specific allowance, average recorded investment	1,053	1,400	1,122	960	1,167
Impaired loans with no specific allowance, interest income recognized in period	10	40	24	54	76
Impaired loans with no specific allowance, cash basis interest recognized in period	10	24	24	37	66
Commercial Portfolio Segment [Member]
Impaired loans with specific allowance, unpaid principal balance	4	72	4	72	78
Impaired loans with specific allowance, recorded investment	4	72	4	72	78
Related allowance	4	11	4	11	20
Impaired loans with specific allowance, average recorded investment	33	58	48	39	53
Impaired loans with specific allowance, interest income recognized in period	0	0	0	1	5
Impaired loans with specific allowance, cash basis interest recognized in period	0	0	0	1	4
Impaired loans with no specific allowance, unpaid principal balance	120	141	120	141	65
Impaired loans with no specific allowance, recorded investment	120	141	120	141	65
Impaired loans with no specific allowance, average recorded investment	93	92	84	75	80
Impaired loans with no specific allowance, interest income recognized in period	2	4	3	4	10
Impaired loans with no specific allowance, cash basis interest recognized in period	2	2	3	2	6
Consumer Portfolio Segment [Member]
Impaired loans with specific allowance, unpaid principal balance	0	0	0	0	0
Impaired loans with specific allowance, recorded investment	0	0	0	0	0
Related allowance	0	0	0	0	0
Impaired loans with specific allowance, average recorded investment	0	0	0	0	0
Impaired loans with specific allowance, interest income recognized in period	0	0	0	0	0
Impaired loans with specific allowance, cash basis interest recognized in period	0	0	0	0	0
Impaired loans with no specific allowance, unpaid principal balance	0	0	0	0	0
Impaired loans with no specific allowance, recorded investment	0	0	0	0	0
Impaired loans with no specific allowance, average recorded investment	0	0	0	0	0
Impaired loans with no specific allowance, interest income recognized in period	0	0	0	0	0
Impaired loans with no specific allowance, cash basis interest recognized in period	$ 0	$ 0	$ 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
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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.

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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.

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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
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-URI http://asc.fasb.org/extlink&oid=123577603&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.

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

+ References

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-Publisher FASB
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-URI http://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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