Note 9 - Allowance for Loan Losses and Credit Quality Information - Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Dec. 31, 2017
Balance	$ 9,129	$ 9,590	$ 9,311	$ 9,903
Provision for losses	295	269	170	(1)
Charge-offs	(311)	(17)	(403)	(218)
Recoveries	215	203	250	361
Balance	9,328	10,045	9,328	10,045
Specific allowance					$ 794	$ 1,073
General allowance					8,534	8,238
Balance	9,328	9,590	9,328	10,045	9,328	9,311
Individually reviewed for impairment					3,975	4,274
Collectively reviewed for impairment					594,808	590,524
Ending balance					598,783	594,798
Residential Portfolio Segment [Member]
Balance	809	1,110	900	1,186
Provision for losses	72	(106)	4	(182)
Charge-offs	0	0	(23)	0
Recoveries	0	0	0	0
Balance	881	1,004	881	1,004
Specific allowance					110	192
General allowance					771	708
Balance	809	1,110	881	1,004	881	900
Individually reviewed for impairment					1,294	1,523
Collectively reviewed for impairment					105,909	105,482
Ending balance					107,203	107,005
Commercial Real Estate Portfolio Segment [Member]
Balance	5,198	4,958	5,073	4,953
Provision for losses	(147)	452	(29)	363
Charge-offs	0	0	0	0
Recoveries	191	80	198	174
Balance	5,242	5,490	5,242	5,490
Specific allowance					437	441
General allowance					4,805	4,632
Balance	5,198	4,958	5,242	5,490	5,242	5,073
Individually reviewed for impairment					1,432	1,364
Collectively reviewed for impairment					336,728	332,753
Ending balance					338,160	334,117
Consumer Portfolio Segment [Member]
Balance	1,423	1,332	1,630	1,613
Provision for losses	254	224	109	116
Charge-offs	(56)	(17)	(125)	(218)
Recoveries	2	5	9	33
Balance	1,623	1,544	1,623	1,544
Specific allowance					173	263
General allowance					1,450	1,367
Balance	1,423	1,332	1,623	1,544	1,623	1,630
Individually reviewed for impairment					984	880
Collectively reviewed for impairment					71,306	72,887
Ending balance					72,290	73,767
Commercial Portfolio Segment [Member]
Balance	1,699	2,190	1,708	2,151
Provision for losses	116	(301)	86	(298)
Charge-offs	(255)	0	(255)	0
Recoveries	22	118	43	154
Balance	1,582	2,007	1,582	2,007
Specific allowance					74	177
General allowance					1,508	1,531
Balance	$ 1,699	$ 2,190	$ 1,582	$ 2,007	1,582	1,708
Individually reviewed for impairment					265	507
Collectively reviewed for impairment					80,865	79,402
Ending balance					$ 81,130	$ 79,909