Note 5 - Loans Receivable and Related Allowance for Loan Losses - Impaired Loans by Class (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Impaired loans with specific allowance, unpaid principal balance	$ 80	$ 76	$ 80	$ 76	$ 83
Impaired loans with specific allowance, recorded investment	80	76	80	76	83
Related allowance	7	8	7	8	7
Impaired loans with specific allowance, average recorded investment	81	76	82	377	319
Impaired loans with specific allowance, interest income recognized in period	1		2	2	3
Impaired loans with specific allowance, cash basis interest recognized in period	1		2	2	3
Impaired loans with no specific allowance, unpaid principal balance	2,989	2,167	2,989	2,167	2,119
Impaired loans with no specific allowance, recorded investment	2,878	1,881	2,878	1,881	1,833
Impaired loans with no specific allowance, average recorded investment	1,647	1,911	1,590	1,595	1,642
Impaired loans with no specific allowance, interest income recognized in period	86	3	202	9	14
Impaired loans with no specific allowance, cash basis interest recognized in period	5	3	119	9	14
Residential Portfolio Segment [Member]
Impaired loans with specific allowance, unpaid principal balance	74	76	74	76	75
Impaired loans with specific allowance, recorded investment	74	76	74	76	75
Related allowance	7	8	7	8	7
Impaired loans with specific allowance, average recorded investment	74	76	75	91	88
Impaired loans with specific allowance, interest income recognized in period	1		2	2	3
Impaired loans with specific allowance, cash basis interest recognized in period	1		2	2	3
Impaired loans with no specific allowance, unpaid principal balance	438	469	438	469	461
Impaired loans with no specific allowance, recorded investment	327	357	327	357	350
Impaired loans with no specific allowance, average recorded investment	330	362	338	274	289
Impaired loans with no specific allowance, interest income recognized in period	2	1	3	5	8
Impaired loans with no specific allowance, cash basis interest recognized in period	2	1	3	5	8
Home Equity Loans and Lines of Credit [Member]
Impaired loans with specific allowance, unpaid principal balance	6		6		8
Impaired loans with specific allowance, recorded investment	6		6		8
Related allowance
Impaired loans with specific allowance, average recorded investment	7		7		2
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
Commercial Real Estate 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				139	111
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	2,512	1,113	2,512	1,113	1,089
Impaired loans with no specific allowance, recorded investment	2,512	939	2,512	939	914
Impaired loans with no specific allowance, average recorded investment	1,278	957	952	840	855
Impaired loans with no specific allowance, interest income recognized in period	83	1	125	2	3
Impaired loans with no specific allowance, cash basis interest recognized in period	2	1	42	2	3
Commercial 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				147	118
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	39	585	39	585	569
Impaired loans with no specific allowance, recorded investment	39	585	39	585	569
Impaired loans with no specific allowance, average recorded investment	39	592	300	481	498
Impaired loans with no specific allowance, interest income recognized in period	1	1	74	2	3
Impaired loans with no specific allowance, cash basis interest recognized in period	1	1	74	2	3
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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- 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.

+ 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

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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=84173941&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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- 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=84173941&loc=d3e5212-111524

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=84173941&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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