Note 9 - Allowance for Loan Losses and Credit Quality Information - Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Dec. 31, 2017
Balance	$ 9,311	$ 9,903
Provision for losses	(125)	(270)
Charge-offs	(92)	(201)
Recoveries	35	158
Balance	9,129	9,590
Specific reserves			$ 948	$ 1,073
General reserves			8,181	8,238
Balance	9,129	9,903	9,129	9,311
Individually reviewed for impairment			4,035	4,274
Collectively reviewed for impairment			596,503	590,524
Ending balance			600,538	594,798
Residential Portfolio Segment [Member]
Balance	900	1,186
Provision for losses	(68)	(76)
Charge-offs	(23)	0
Recoveries	0	0
Balance	809	1,110
Specific reserves			99	192
General reserves			710	708
Balance	900	1,186	809	900
Individually reviewed for impairment			1,172	1,523
Collectively reviewed for impairment			105,883	105,482
Ending balance			107,055	107,005
Commercial Real Estate Portfolio Segment [Member]
Balance	5,073	4,953
Provision for losses	118	(90)
Charge-offs	0	0
Recoveries	7	95
Balance	5,198	4,958
Specific reserves			445	441
General reserves			4,753	4,632
Balance	5,073	4,953	5,198	5,073
Individually reviewed for impairment			1,524	1,364
Collectively reviewed for impairment			342,307	332,753
Ending balance			343,831	334,117
Consumer Portfolio Segment [Member]
Balance	1,630	1,613
Provision for losses	(145)	(108)
Charge-offs	(69)	(201)
Recoveries	7	28
Balance	1,423	1,332
Specific reserves			239	263
General reserves			1,184	1,367
Balance	1,630	1,613	1,423	1,630
Individually reviewed for impairment			859	880
Collectively reviewed for impairment			71,911	72,887
Ending balance			72,770	73,767
Commercial Portfolio Segment [Member]
Balance	1,708	2,151
Provision for losses	(30)	4
Charge-offs	0	0
Recoveries	21	35
Balance	1,699	2,190
Specific reserves			165	177
General reserves			1,534	1,531
Balance	$ 1,708	$ 2,151	1,699	1,708
Individually reviewed for impairment			480	507
Collectively reviewed for impairment			76,402	79,402
Ending balance			$ 76,882	$ 79,909