Note 9 - Allowance for Loan Losses and Credit Quality Information - Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Dec. 31, 2017
Balance	$ 9,328	$ 10,045	$ 9,311	$ 9,903
Provision for loan losses	(652)	(581)	(482)	(582)
Charge-offs	(31)	(351)	(435)	(569)
Recoveries	187	164	438	525
Balance	8,832	9,277	8,832	9,277
Specific reserves					$ 1,061	$ 1,073
General reserves					7,771	8,238
Balance	8,832	10,045	8,832	9,277	8,832	9,311
Individually reviewed for impairment					6,413	4,274
Collectively reviewed for impairment					587,986	590,524
Ending balance					594,399	594,798
Residential Portfolio Segment [Member]
Balance	881	1,004	900	1,186
Provision for loan losses	(10)	(63)	(6)	(245)
Charge-offs	0	(6)	(24)	(6)
Recoveries	0	0	1	0
Balance	871	935	871	935
Specific reserves					104	192
General reserves					767	708
Balance	881	1,004	871	935	871	900
Individually reviewed for impairment					1,407	1,523
Collectively reviewed for impairment					107,086	105,482
Ending balance					108,493	107,005
Commercial Real Estate Portfolio Segment [Member]
Balance	5,242	5,490	5,073	4,953
Provision for loan losses	(287)	(509)	(316)	(147)
Charge-offs	0	0	0	0
Recoveries	0	32	198	207
Balance	4,955	5,013	4,955	5,013
Specific reserves					688	441
General reserves					4,267	4,632
Balance	5,242	5,490	4,955	5,013	4,955	5,073
Individually reviewed for impairment					3,689	1,364
Collectively reviewed for impairment					328,814	332,753
Ending balance					332,503	334,117
Consumer Portfolio Segment [Member]
Balance	1,623	1,544	1,630	1,613
Provision for loan losses	61	141	169	257
Charge-offs	(16)	(45)	(141)	(263)
Recoveries	5	6	15	39
Balance	1,673	1,646	1,673	1,646
Specific reserves					187	263
General reserves					1,486	1,367
Balance	1,623	1,544	1,673	1,646	1,673	1,630
Individually reviewed for impairment					946	880
Collectively reviewed for impairment					73,575	72,887
Ending balance					74,521	73,767
Commercial Portfolio Segment [Member]
Balance	1,582	2,007	1,708	2,151
Provision for loan losses	(416)	(150)	(329)	(447)
Charge-offs	(15)	(300)	(270)	(300)
Recoveries	182	126	224	279
Balance	1,333	1,683	1,333	1,683
Specific reserves					82	177
General reserves					1,251	1,531
Balance	$ 1,582	$ 2,007	$ 1,333	$ 1,683	1,333	1,708
Individually reviewed for impairment					371	507
Collectively reviewed for impairment					78,511	79,402
Ending balance					$ 78,882	$ 79,909