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Note 5 - Loans Receivable and Related Allowance for Loan Losses - Activity in Allowance for Loan Losses by Portfolio (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	Sep. 30, 2018	Dec. 31, 2017
Beginning Balance	$ 6,118	$ 5,767	$ 6,127	$ 5,545	$ 5,545
Charge-offs	(76)	(101)	(807)	(275)
Recoveries	18	4	60	37
Provision	300	270	980	633
Ending Balance	6,360	5,940	6,360	5,940	6,127
Individually evaluated for impairment						$ 7	$ 7
Acquired loans
Collectively evaluated for impairment						6,353	6,120
Total	6,360	5,767	6,360	5,940	6,127	6,360	6,127
Individually evaluated for impairment						2,958	1,916
Acquired loans			53,226		62,921
Collectively evaluated for impairment						542,301	518,524
Loans, gross						598,485	583,361
Residential Portfolio Segment [Member]
Beginning Balance	2,033	1,994	2,090	1,846	1,846
Charge-offs		(2)	(61)	(38)
Recoveries			3
Provision	128	46	129	230
Ending Balance	2,161	2,038	2,161	2,038	2,090
Individually evaluated for impairment						7	7
Acquired loans
Collectively evaluated for impairment						2,154	2,083
Total	2,033	1,994	2,161	2,038	2,090	2,161	2,090
Individually evaluated for impairment						401	425
Acquired loans			17,767		20,300
Collectively evaluated for impairment						218,938	201,098
Loans, gross						237,106	221,823
Home Equity Loans and Lines of Credit [Member]
Beginning Balance	650	639	646	633	633
Charge-offs	(26)	(33)	(109)	(44)
Recoveries	1	1	12	21
Provision	34	20	110	17
Ending Balance	659	627	659	627	646
Individually evaluated for impairment
Acquired loans
Collectively evaluated for impairment						659	646
Total	650	639	659	627	646	659	646
Individually evaluated for impairment						6	8
Acquired loans			9,817		10,873
Collectively evaluated for impairment						89,845	89,059
Loans, gross						99,668	99,940
Commercial Real Estate Portfolio Segment [Member]
Beginning Balance	2,882	2,460	2,753	2,314	2,314
Charge-offs	(6)	(36)	(424)	(126)
Recoveries	13	2	32	6
Provision	81	200	609	432
Ending Balance	2,970	2,626	2,970	2,626	2,753
Individually evaluated for impairment
Acquired loans
Collectively evaluated for impairment						2,970	2,753
Total	2,882	2,460	2,970	2,626	2,753	2,970	2,753
Individually evaluated for impairment						2,512	914
Acquired loans			22,784		27,404
Collectively evaluated for impairment						174,873	164,750
Loans, gross						200,169	193,068
Commercial Portfolio Segment [Member]
Beginning Balance	499	621	585	700	700
Charge-offs		(4)		(14)
Recoveries			1
Provision	11	(21)	(76)	(90)
Ending Balance	510	596	510	596	585
Individually evaluated for impairment
Acquired loans
Collectively evaluated for impairment						510	585
Total	499	621	510	596	585	510	585
Individually evaluated for impairment						39	569
Acquired loans			1,778		1,451
Collectively evaluated for impairment						50,777	56,921
Loans, gross						52,594	58,941
Consumer Portfolio Segment [Member]
Beginning Balance	54	53	53	52	52
Charge-offs	(44)	(26)	(213)	(53)
Recoveries	4	1	12	10
Provision	46	25	208	44
Ending Balance	60	53	60	53	53
Individually evaluated for impairment
Acquired loans
Collectively evaluated for impairment						60	53
Total	$ 54	$ 53	60	$ 53	53	60	53
Individually evaluated for impairment
Acquired loans			$ 1,080		$ 2,893
Collectively evaluated for impairment						7,868	6,696
Loans, gross						$ 8,948	$ 9,589