Note 26 - Quarterly Operating Results (Unaudited) - Quarterly Operating Results (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest income	$ 29,092	$ 28,111	$ 27,013	$ 26,633	$ 26,368	$ 25,942	$ 25,162	$ 24,700	$ 24,039	$ 23,284	$ 23,000	$ 22,847	$ 110,849	$ 102,172	$ 93,170
Interest expense	2,069	1,947	1,781	1,449	1,293	1,182	1,212	1,231	1,217	1,203	1,199	1,233	7,246	4,918	4,852
Net interest income	27,023	26,164	25,232	25,184	25,075	24,760	23,950	23,469	22,822	22,081	21,801	21,614	103,603	97,254	88,318
Provision for loan losses	900	150	600	900	500	1,250	750	500	750				2,550	3,000	750
Net interest income after provision	26,123	26,014	24,632	24,284	24,575	23,510	23,200	22,969	22,072	22,081	21,801	21,614	101,053	94,254	87,568
Non-interest income	11,545	11,103	11,675	10,797	11,319	11,358	10,778	10,082	10,073	9,985	10,219	9,673	45,120	43,537	39,950
Non-interest expenses	27,180	21,317	21,346	21,148	21,269	20,518	20,193	19,540	18,322	18,430	18,867	17,779	90,991	81,520	73,398
Income before income taxes	10,488	15,800	14,961	13,933	14,625	14,350	13,785	13,511	13,823	13,636	13,153	13,508	55,182	56,271	54,120
Income tax expense	5,542	4,096	4,359	3,142	4,009	3,883	3,676	3,676	4,177	4,352	4,151	4,253	$ 17,139	$ 15,244	$ 16,933
Net income	$ 4,946	$ 11,704	$ 10,602	$ 10,791	$ 10,616	$ 10,467	$ 10,109	$ 9,835	$ 9,646	$ 9,284	$ 9,002	$ 9,255
Basic earnings per share (in dollars per share)	$ 0.22	$ 0.52	$ 0.47	$ 0.48	$ 0.47	$ 0.47	$ 0.45	$ 0.44	$ 0.43	$ 0.42	$ 0.41	$ 0.42	$ 1.69	$ 1.84	$ 1.68
Diluted earnings per share (in dollars per share)	$ 0.22	$ 0.51	$ 0.46	$ 0.47	$ 0.46	$ 0.46	$ 0.45	$ 0.44	$ 0.43	$ 0.41	$ 0.40	$ 0.42	$ 1.66	$ 1.80	$ 1.65