Note 19 - Segments - Financial Information by Business Segment (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Net interest income	$ 27,295	$ 25,184
Provision for loan losses	735	900	$ 2,550
All other non-interest income	5,423	5,550
Non-interest expense	21,027	20,995
Income before income taxes	16,456	13,933
Income tax expense	3,052	3,142
Net income	13,404	10,791
Segment assets	3,285,480	3,033,343	$ 3,239,646
Fiduciary and Trust [Member]
Non-interest income	5,500	5,094
Commercial Banking [Member]
Net interest income	27,224	25,107
Provision for loan losses	735	900
All other non-interest income	5,423	5,500
Non-interest expense	17,829	17,948
Income before income taxes	14,083	11,809
Income tax expense	2,537	2,384
Net income	11,546	9,425
Segment assets	3,283,539	3,031,318
Commercial Banking [Member] | Fiduciary and Trust [Member]
Non-interest income
Investment Management and Trust [Member]
Net interest income	71	77
Provision for loan losses
All other non-interest income
Non-interest expense	3,198	3,047
Income before income taxes	2,373	2,124
Income tax expense	515	758
Net income	1,858	1,366
Segment assets	1,941	2,025
Investment Management and Trust [Member] | Fiduciary and Trust [Member]
Non-interest income	$ 5,500	$ 5,094