Note 5 - Loans Receivable and Allowance for Loan Losses - Impaired Loans (Details) - USD ($)	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Impaired loans, related allowance	$ 55,000		$ 55,000		$ 253,000
Impaired loans, recorded investment	9,300,000		9,300,000		6,800,000
Business Activities Loans [Member]
Impaired loans with no related allowance recorded, recorded investment	9,258,000		9,258,000		6,500,000
Impaired loans with no related allowance recorded, unpaid principal balance	10,628,000		10,628,000		7,295,000
Impaired loans with a related allowance recorded, recorded investment	69,000		69,000		253,000
Impaired loans with a related allowance recorded, unpaid principal balance	119,000		119,000		253,000
Impaired loans, related allowance	55,000		55,000		253,000
Impaired loans, recorded investment	9,327,000		9,327,000		6,753,000
Impaired loans, unpaid principal balance	10,747,000		10,747,000		7,548,000
Impaired loans with no related allowance recorded, average recorded investment	9,374,000	$ 8,635,000	8,295,000	$ 8,684,000
Impaired loans with no allowance recorded, interest income recognized	32,000	10,000	101,000	174,000
Impaired loans with a related allowance recorded, average recorded investment	50,000	245,000	189,000	237,000
Impaired loans with a related allowance recorded, interest income recognized
Impaired loans, average recorded investment	9,424,000	8,880,000	8,484,000	8,921,000
Impaired loans, interest income recognized	32,000	10,000	101,000	174,000
Commercial Real Estate Portfolio Segment [Member] \| Business Activities Loans [Member]
Impaired loans with no related allowance recorded, recorded investment	3,989,000		3,989,000		1,977,000
Impaired loans with no related allowance recorded, unpaid principal balance	4,481,000		4,481,000		2,425,000
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	3,989,000		3,989,000		1,977,000
Impaired loans, unpaid principal balance	4,481,000		4,481,000		2,425,000
Impaired loans with no related allowance recorded, average recorded investment	4,062,000	6,111,000	3,157,000	6,173,000
Impaired loans with no allowance recorded, interest income recognized	21,000	10,000	70,000	159,000
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	4,062,000	6,111,000	3,157,000	6,173,000
Impaired loans, interest income recognized	21,000	10,000	70,000	159,000
Residential Portfolio Segment [Member] \| Business Activities Loans [Member]
Impaired loans with no related allowance recorded, recorded investment	3,521,000		3,521,000		3,336,000
Impaired loans with no related allowance recorded, unpaid principal balance	3,554,000		3,554,000		3,369,000
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	3,521,000		3,521,000		3,336,000
Impaired loans, unpaid principal balance	3,554,000		3,554,000		3,369,000
Impaired loans with no related allowance recorded, average recorded investment	3,523,000	1,903,000	3,451,000	1,907,000
Impaired loans with no allowance recorded, interest income recognized	3,000		8,000	5,000
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	3,523,000	1,903,000	3,451,000	1,907,000
Impaired loans, interest income recognized	3,000		8,000	5,000
Commercial Portfolio Segment [Member] \| Business Activities Loans [Member]
Impaired loans with no related allowance recorded, recorded investment	980,000		980,000		497,000
Impaired loans with no related allowance recorded, unpaid principal balance	1,751,000		1,751,000		683,000
Impaired loans with a related allowance recorded, recorded investment	48,000		48,000		251,000
Impaired loans with a related allowance recorded, unpaid principal balance	98,000		98,000		251,000
Impaired loans, related allowance	48,000		48,000		251,000
Impaired loans, recorded investment	1,028,000		1,028,000		748,000
Impaired loans, unpaid principal balance	1,849,000		1,849,000		934,000
Impaired loans with no related allowance recorded, average recorded investment	1,018,000	37,000	948,000	46,000
Impaired loans with no allowance recorded, interest income recognized
Impaired loans with a related allowance recorded, average recorded investment	45,000	245,000	185,000	237,000
Impaired loans with a related allowance recorded, interest income recognized
Impaired loans, average recorded investment	1,063,000	282,000	1,133,000	283,000
Impaired loans, interest income recognized
Consumer Portfolio Segment [Member] \| Business Activities Loans [Member]
Impaired loans with no related allowance recorded, recorded investment	768,000		768,000		690,000
Impaired loans with no related allowance recorded, unpaid principal balance	842,000		842,000		818,000
Impaired loans with a related allowance recorded, recorded investment	21,000		21,000		2,000
Impaired loans with a related allowance recorded, unpaid principal balance	21,000		21,000		2,000
Impaired loans, related allowance	7,000		7,000		2,000
Impaired loans, recorded investment	789,000		789,000		692,000
Impaired loans, unpaid principal balance	863,000		863,000		$ 820,000
Impaired loans with no related allowance recorded, average recorded investment	771,000	584,000	739,000	558,000
Impaired loans with no allowance recorded, interest income recognized	8,000		23,000	10,000
Impaired loans with a related allowance recorded, average recorded investment	5,000		4,000
Impaired loans with a related allowance recorded, interest income recognized
Impaired loans, average recorded investment	776,000	584,000	743,000	558,000
Impaired loans, interest income recognized	$ 8,000		$ 23,000	$ 10,000

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://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

Reference 2: 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=84173941&loc=d3e5258-111524

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