Note 9 - Loans - Aging of Loan Portfolio (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Loans	$ 17,398,357	$ 16,342,479
Financial Asset, 30 to 59 Days Past Due [Member]
Loans	112,998	32,812
Financial Asset, 60 to 89 Days Past Due [Member]
Loans	3,495	13,015
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Loans	300	1,439
Financial Asset, Past Due [Member]
Loans	203,126	113,112
Non-accrual loans	86,333	65,846
Financial Asset, Not Past Due [Member]
Loans	17,195,231	16,229,367
Commercial Portfolio Segment [Member]
Loans	3,125,151	2,982,399
Commercial Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Loans	15,757	4,294
Commercial Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Loans	1,886	9,877
Commercial Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Loans	300	1,439
Commercial Portfolio Segment [Member] | Financial Asset, Past Due [Member]
Loans	54,225	32,168
Non-accrual loans	36,282	16,558
Commercial Portfolio Segment [Member] | Financial Asset, Not Past Due [Member]
Loans	3,070,926	2,950,231
Real Estate Construction Portfolio Segment [Member]
Loans	631,740	611,031
Real Estate Construction Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Loans	0	0
Real Estate Construction Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Loans	0	0
Real Estate Construction Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Loans	0	0
Real Estate Construction Portfolio Segment [Member] | Financial Asset, Past Due [Member]
Loans	0	0
Non-accrual loans	0	0
Real Estate Construction Portfolio Segment [Member] | Financial Asset, Not Past Due [Member]
Loans	631,740	611,031
Commercial Real Estate Portfolio Segment [Member]
Loans	8,401,742	8,143,272
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Loans	5,582	8,389
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Loans	0	0
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Loans	0	0
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, Past Due [Member]
Loans	43,677	46,562
Non-accrual loans	38,095	38,173
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, Not Past Due [Member]
Loans	8,358,065	8,096,710
Residential Mortgage and Equity Lines Portfolio Segment [Member]
Loans	5,233,633	4,601,493
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Loans	91,465	20,129
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Loans	1,609	3,138
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Loans	0	0
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Financial Asset, Past Due [Member]
Loans	105,030	34,382
Non-accrual loans	11,956	11,115
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Financial Asset, Not Past Due [Member]
Loans	5,128,603	4,567,111
Installment and Other Loans [Member ]
Loans	6,091	4,284
Installment and Other Loans [Member ] | Financial Asset, 30 to 59 Days Past Due [Member]
Loans	194	0
Installment and Other Loans [Member ] | Financial Asset, 60 to 89 Days Past Due [Member]
Loans	0	0
Installment and Other Loans [Member ] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Loans	0	0
Installment and Other Loans [Member ] | Financial Asset, Past Due [Member]
Loans	194	0
Non-accrual loans	0	0
Installment and Other Loans [Member ] | Financial Asset, Not Past Due [Member]
Loans	$ 5,897	$ 4,284