Note 8 - Loans - Allowance for Loan Losses by Portfolio Segment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Beginning Balance	$ 148,273	$ 122,555	$ 123,224	$ 122,391
Provision for possible credit losses	25,000	0	50,000	0
Charge-offs	(5,106)	(1,713)	(6,427)	(2,944)
Recoveries	1,513	1,809	2,883	3,204
Net (charge-offs)/recoveries	(3,593)	96	(3,544)	260
Ending Balance	169,680	122,651	169,680	122,651
Reserve for impaired loans	7,525	1,686	7,525	1,686
Reserve for non-impaired loans	162,155	120,965	162,155	120,965
Reserve for off-balance sheet credit commitments	4,663	4,550	4,663	4,550
Commercial Portfolio Segment [Member]
Beginning Balance	67,799	54,750	57,021	54,978
Provision for possible credit losses	18,213	(100)	29,104	862
Charge-offs	(5,106)	(1,713)	(6,427)	(2,944)
Recoveries	1,350	1,356	2,558	1,397
Net (charge-offs)/recoveries	(3,756)	(357)	(3,869)	(1,547)
Ending Balance	82,256	54,293	82,256	54,293
Reserve for impaired loans	6,895	832	6,895	832
Reserve for non-impaired loans	75,361	53,461	75,361	53,461
Reserve for off-balance sheet credit commitments	3,581	2,090	3,581	2,090
Real Estate Construction Portfolio Segment [Member]
Beginning Balance	23,222	20,723	19,474	19,626
Provision for possible credit losses	3,478	257	7,226	310
Charge-offs	0	0	0	0
Recoveries	0	30	0	1,074
Net (charge-offs)/recoveries	0	30	0	1,074
Ending Balance	26,700	21,010	26,700	21,010
Reserve for impaired loans	0	0	0	0
Reserve for non-impaired loans	26,700	21,010	26,700	21,010
Reserve for off-balance sheet credit commitments	666	2,029	666	2,029
Commercial Real Estate Portfolio Segment [Member]
Beginning Balance	39,886	33,073	33,602	33,487
Provision for possible credit losses	1,151	(180)	7,280	(746)
Charge-offs	0	0	0	0
Recoveries	95	261	250	413
Net (charge-offs)/recoveries	95	261	250	413
Ending Balance	41,132	33,154	41,132	33,154
Reserve for impaired loans	323	620	323	620
Reserve for non-impaired loans	40,809	32,534	40,809	32,534
Reserve for off-balance sheet credit commitments	117	137	117	137
Residential Mortgage and Equity Lines Portfolio Segment [Member]
Beginning Balance	17,366	13,975	13,108	14,282
Provision for possible credit losses	2,158	27	6,409	(438)
Charge-offs	0	0	0	0
Recoveries	68	162	75	320
Net (charge-offs)/recoveries	68	162	75	320
Ending Balance	19,592	14,164	19,592	14,164
Reserve for impaired loans	307	234	307	234
Reserve for non-impaired loans	19,285	13,930	19,285	13,930
Reserve for off-balance sheet credit commitments	297	290	297	290
Installment and Other Loans [Member ]
Beginning Balance	0	34	19	18
Provision for possible credit losses	0	(4)	(19)	12
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Net (charge-offs)/recoveries	0	0	0	0
Ending Balance	0	30	0	30
Reserve for impaired loans	0	0	0	0
Reserve for non-impaired loans	0	30	0	30
Reserve for off-balance sheet credit commitments	$ 2	$ 4	$ 2	$ 4