Note 3 - Loans Receivable and Allowance for Loan Losses - Impaired Loans (Details) - USD ($)	3 Months Ended	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Impaired loans with no related allowance recorded, recorded investment	$ 8,700,000		$ 8,700,000		$ 8,720,000
Impaired loans with no related allowance recorded, unpaid principal balance	9,817,000		9,817,000		10,267,000
Impaired loans with a related allowance recorded, recorded investment	285,000		285,000		231,000
Impaired loans with a related allowance recorded, unpaid principal balance	285,000		285,000		231,000
Impaired loans, related allowance	285,000		285,000		231,000
Impaired loans, recorded investment	8,985,000		8,985,000		8,951,000
Impaired loans, unpaid principal balance	10,102,000		10,102,000		10,498,000
Impaired loans with no related allowance recorded, average recorded investment	8,635,000	$ 11,635,000	8,684,000	$ 12,430,000
Impaired loans with no allowance recorded, interest income recognized	10,000	113,000	174,000	343,000
Impaired loans with a related allowance recorded, average recorded investment	245,000	3,070,000	237,000	2,280,000
Impaired loans with a related allowance recorded, interest income recognized
Impaired loans, average recorded investment	8,880,000	14,705,000	8,921,000	14,710,000
Impaired loans, interest income recognized	10,000	113,000	174,000	343,000
Commercial Real Estate Portfolio Segment [Member]
Impaired loans with no related allowance recorded, recorded investment	6,081,000		6,081,000		6,267,000
Impaired loans with no related allowance recorded, unpaid principal balance	6,531,000		6,531,000		6,721,000
Impaired loans with a related allowance recorded, recorded investment
Impaired loans with a related allowance recorded, unpaid principal balance
Impaired loans, related allowance
Impaired loans, recorded investment	6,081,000		6,081,000		6,267,000
Impaired loans, unpaid principal balance	6,531,000		6,531,000		6,721,000
Impaired loans with no related allowance recorded, average recorded investment	6,111,000	6,428,000	6,173,000	7,281,000
Impaired loans with no allowance recorded, interest income recognized	10,000	77,000	159,000	236,000
Impaired loans with a related allowance recorded, average recorded investment
Impaired loans with a related allowance recorded, interest income recognized
Impaired loans, average recorded investment	6,111,000	6,428,000	6,173,000	7,281,000
Impaired loans, interest income recognized	10,000	77,000	159,000	236,000
Residential Portfolio Segment [Member]
Impaired loans with no related allowance recorded, recorded investment	1,904,000		1,904,000		1,911,000
Impaired loans with no related allowance recorded, unpaid principal balance	1,935,000		1,935,000		2,915,000
Impaired loans with a related allowance recorded, recorded investment
Impaired loans with a related allowance recorded, unpaid principal balance
Impaired loans, related allowance
Impaired loans, recorded investment	1,904,000		1,904,000		1,911,000
Impaired loans, unpaid principal balance	1,935,000		1,935,000		2,915,000
Impaired loans with no related allowance recorded, average recorded investment	1,903,000	4,787,000	1,907,000	4,666,000
Impaired loans with no allowance recorded, interest income recognized		36,000	5,000	98,000
Impaired loans with a related allowance recorded, average recorded investment
Impaired loans with a related allowance recorded, interest income recognized
Impaired loans, average recorded investment	1,903,000	4,787,000	1,907,000	4,666,000
Impaired loans, interest income recognized		36,000	5,000	98,000
Commercial Portfolio Segment [Member]
Impaired loans with no related allowance recorded, recorded investment
Impaired loans with no related allowance recorded, unpaid principal balance	503,000		503,000
Impaired loans with a related allowance recorded, recorded investment	285,000		285,000		231,000
Impaired loans with a related allowance recorded, unpaid principal balance	285,000		285,000		231,000
Impaired loans, related allowance	285,000		285,000		231,000
Impaired loans, recorded investment	285,000		285,000		231,000
Impaired loans, unpaid principal balance	788,000		788,000		231,000
Impaired loans with no related allowance recorded, average recorded investment	37,000	148,000	46,000	74,000
Impaired loans with no allowance recorded, interest income recognized
Impaired loans with a related allowance recorded, average recorded investment	245,000	3,068,000	237,000	2,278,000
Impaired loans with a related allowance recorded, interest income recognized
Impaired loans, average recorded investment	282,000	3,216,000	283,000	2,352,000
Impaired loans, interest income recognized
Consumer Portfolio Segment [Member]
Impaired loans with no related allowance recorded, recorded investment	715,000		715,000		542,000
Impaired loans with no related allowance recorded, unpaid principal balance	809,000		809,000		631,000
Impaired loans with a related allowance recorded, recorded investment
Impaired loans with a related allowance recorded, unpaid principal balance
Impaired loans, related allowance
Impaired loans, recorded investment	715,000		715,000		542,000
Impaired loans, unpaid principal balance	809,000		809,000		631,000
Impaired loans with no related allowance recorded, average recorded investment	584,000	272,000	558,000	409,000
Impaired loans with no allowance recorded, interest income recognized			10,000	9,000
Impaired loans with a related allowance recorded, average recorded investment		2,000		2,000
Impaired loans with a related allowance recorded, interest income recognized
Impaired loans, average recorded investment	584,000	274,000	558,000	411,000
Impaired loans, interest income recognized			10,000	$ 9,000
Construction Portfolio Segment [Member]
Impaired loans with no related allowance recorded, recorded investment
Impaired loans with no related allowance recorded, unpaid principal balance	39,000		39,000
Impaired loans with a related allowance recorded, recorded investment
Impaired loans with a related allowance recorded, unpaid principal balance
Impaired loans, related allowance
Impaired loans, recorded investment
Impaired loans, unpaid principal balance	$ 39,000		$ 39,000

Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-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

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-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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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-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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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-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

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5212-111524

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