Note 5 - Loans - Allowance for Credit Losses and Recorded Investment in Financing Receivables (Details) - USD ($) $ in Thousands	3 Months Ended				12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Balance				$ 11,544	$ 11,925	$ 11,544	$ 11,180
Charge-offs					(1,248)	(1,502)	(2,784)
Recoveries					1,615	933	3,148
Provision for loan and lease losses	$ 450		$ 300	200		950
Balance	11,925				12,292	11,925	11,544
Individually evaluated for impairment								$ 1,237	$ 1,169	$ 1,461
Collectively evaluated for impairment								11,055	10,756	10,083
Total	11,925			11,544	11,925	11,925	11,544	12,292	11,925	11,544
Individually evaluated for impairment								11,012	13,147	18,794
Collectively evaluated for impairment								935,239	866,688	785,417
Total gross loans								946,251	879,835	804,211
Commercial Portfolio Segment [Member]
Balance				2,747	2,397	2,747	2,493
Charge-offs					(132)	(51)	(1,106)
Recoveries					865	512	427
Provision for loan and lease losses					(925)	(811)	933
Balance	2,397				2,205	2,397	2,747
Individually evaluated for impairment								748	690	641
Collectively evaluated for impairment								1,457	1,707	2,106
Total	2,397			2,747	2,397	2,397	2,747	2,205	2,397	2,747
Individually evaluated for impairment								2,183	3,154	3,525
Collectively evaluated for impairment								133,360	139,251	143,356
Total gross loans								135,543	142,405	146,881
Commercial Real Estate Portfolio Segment [Member]
Balance				5,680	6,514	5,680	5,784
Charge-offs							(37)
Recoveries						27	2,480
Provision for loan and lease losses					602	807	(2,547)
Balance	6,514				7,116	6,514	5,680
Individually evaluated for impairment								209	77	85
Collectively evaluated for impairment								6,907	6,437	5,595
Total	6,514			5,680	6,514	6,514	5,680	7,116	6,514	5,680
Individually evaluated for impairment								1,343	1,403	3,125
Collectively evaluated for impairment								659,550	584,190	500,580
Total gross loans								660,893	585,593	503,705
Residential Portfolio Segment [Member]
Balance				1,716	1,169	1,716	1,577
Charge-offs					(226)	(483)	(829)
Recoveries					435	178	114
Provision for loan and lease losses					(205)	(242)	854
Balance	1,169				1,173	1,169	1,716
Individually evaluated for impairment								273	391	721
Collectively evaluated for impairment								900	778	995
Total	1,169			1,716	1,169	1,169	1,716	1,173	1,169	1,716
Individually evaluated for impairment								7,463	8,554	11,894
Collectively evaluated for impairment								91,307	93,358	90,050
Total gross loans								98,770	101,912	101,944
Consumer Portfolio Segment [Member]
Balance				955	1,435	955	770
Charge-offs					(890)	(968)	(812)
Recoveries					315	216	127
Provision for loan and lease losses					496	1,232	870
Balance	1,435				1,356	1,435	955
Individually evaluated for impairment								7	11	14
Collectively evaluated for impairment								1,349	1,424	941
Total	1,435			955	1,435	1,435	955	1,356	1,435	955
Individually evaluated for impairment								23	36	250
Collectively evaluated for impairment								51,022	49,889	51,431
Total gross loans								51,045	49,925	51,681
Unallocated Financing Receivables [Member]
Balance				446	410	446	556
Charge-offs
Recoveries
Provision for loan and lease losses					32	(36)	(110)
Balance	410				442	410	446
Individually evaluated for impairment
Collectively evaluated for impairment								442	410	446
Total	$ 410			$ 446	$ 410	$ 410	$ 446	442	410	446
Individually evaluated for impairment
Collectively evaluated for impairment
Total gross loans