Note 18 - Segments - Financial Information by Business Segment (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Net interest income	$ 33,695			$ 32,106			$ 99,669	$ 92,591
Provision for credit losses	4,418	$ 5,500	$ 5,500	400			15,518	1,000
Non-interest income	5,657			5,738			17,601	16,839
All other non-interest income	7,386			7,471			20,600	19,602
Non-interest expenses	26,196			23,898			75,030	71,962
Income before income tax expense	16,124			21,017			47,322	56,070
Income tax expense	1,591			3,783			6,189	6,652
Net income	14,533	$ 13,368	$ 13,232	17,234	$ 16,543	$ 15,641	41,133	49,418
Segment assets	4,365,129			3,533,926			4,365,129	3,533,926	$ 3,724,197
Commercial Banking [Member]
Net interest income	33,619			32,031			99,423	92,356
Provision for credit losses	4,418			400			15,518	1,000
Non-interest income	0			0			0	0
All other non-interest income	7,386			7,471			20,600	19,602
Non-interest expenses	23,062			20,763			65,463	62,627
Income before income tax expense	13,525			18,339			39,042	48,331
Income tax expense	1,027			3,202			4,392	4,973
Net income	12,498			15,137			34,650	43,358
Segment assets	4,361,576			3,530,198			4,361,576	3,530,198
Investment Management and Trust [Member]
Net interest income	76			75			246	235
Provision for credit losses	0			0			0	0
Non-interest income	5,657			5,738			17,601	16,839
All other non-interest income	0			0			0	0
Non-interest expenses	3,134			3,135			9,567	9,335
Income before income tax expense	2,599			2,678			8,280	7,739
Income tax expense	564			581			1,797	1,679
Net income	2,035			2,097			6,483	6,060
Segment assets	$ 3,553			$ 3,728			$ 3,553	$ 3,728