Note 25 - Segments - Financial Information by Business Segment (Details) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
	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, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net interest income	$ 25,075	$ 24,760	$ 23,950	$ 23,469	$ 22,822	$ 22,081	$ 21,801	$ 21,614	$ 21,511	$ 21,363	$ 20,655	$ 20,228	$ 97,254	$ 88,318	$ 83,757
Provision for loan losses	500	1,250	750	500	750					(2,100)	1,350	350	3,000	750	(400)
Investment management and trust services													19,155	18,026	18,212
All other non-interest income													24,382	21,924	20,943
Non-interest expense	21,269	20,518	20,193	19,540	18,322	18,430	18,867	17,779	19,255	18,709	17,701	17,544	81,520	73,398	73,209
Income before income taxes	14,625	14,350	13,785	13,511	13,823	13,636	13,153	13,508	12,029	14,604	11,661	11,809	56,271	54,120	50,103
Income tax expense	4,009	$ 3,883	$ 3,676	$ 3,676	4,177	$ 4,352	$ 4,151	$ 4,253	3,307	$ 4,715	$ 3,627	$ 3,632	15,244	16,933	15,281
Net income													41,027	37,187	34,822
Segment assets	3,039,481				2,816,801				2,563,868				3,039,481	2,816,801	2,563,868
Commercial Banking [Member]
Net interest income													96,986	88,124	83,570
Provision for loan losses													3,000	750	(400)
Investment management and trust services
All other non-interest income													24,382	21,924	20,913
Non-interest expense													70,230	62,748	62,523
Income before income taxes													48,138	46,550	42,360
Income tax expense													12,340	14,238	12,527
Net income													35,798	32,312	29,833
Segment assets	3,037,394				2,816,373				2,563,664				3,037,394	2,816,373	2,563,664
Investment Management and Trust [Member]
Net interest income													268	194	187
Provision for loan losses
Investment management and trust services													19,155	18,026	18,212
All other non-interest income															30
Non-interest expense													11,290	10,650	10,686
Income before income taxes													8,133	7,570	7,743
Income tax expense													2,904	2,695	2,754
Net income													5,229	4,875	4,989
Segment assets	$ 2,087				$ 428				$ 204				$ 2,087	$ 428	$ 204