Note 5 - Loans - Aging of Loan Portfolio (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Loans	$ 18,254,024	$ 16,342,479
Financial Asset, 30 to 59 Days Past Due [Member]
Loans	81,012	32,812
Financial Asset, 60 to 89 Days Past Due [Member]
Loans	8,921	13,015
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Loans	11,580	1,439
Financial Asset, Past Due [Member]
Loans	170,367	113,112
Non-accrual loans	68,854	65,846
Financial Asset, Not Past Due [Member]
Loans	18,083,657	16,229,367
Commercial Portfolio Segment [Member]
Loans	3,318,778	2,982,399
Commercial Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Loans	8,192	4,294
Commercial Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Loans	3,235	9,877
Commercial Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Loans	10,208	1,439
Commercial Portfolio Segment [Member] | Financial Asset, Past Due [Member]
Loans	47,407	32,168
Non-accrual loans	25,772	16,558
Commercial Portfolio Segment [Member] | Financial Asset, Not Past Due [Member]
Loans	3,271,371	2,950,231
Real Estate Construction Portfolio Segment [Member]
Loans	559,372	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	559,372	611,031
Commercial Real Estate Portfolio Segment [Member]
Loans	8,793,685	8,143,272
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Loans	25,772	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	1,372	0
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, Past Due [Member]
Loans	61,240	46,562
Non-accrual loans	34,096	38,173
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, Not Past Due [Member]
Loans	8,732,445	8,096,710
Residential Mortgage and Equity Lines Portfolio Segment [Member]
Loans	5,577,500	4,601,493
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Loans	47,043	20,129
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Loans	5,685	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	61,706	34,382
Non-accrual loans	8,978	11,115
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Financial Asset, Not Past Due [Member]
Loans	5,515,794	4,567,111
Installment and Other Loans [Member ]
Loans	4,689	4,284
Installment and Other Loans [Member ] | Financial Asset, 30 to 59 Days Past Due [Member]
Loans	5	0
Installment and Other Loans [Member ] | Financial Asset, 60 to 89 Days Past Due [Member]
Loans	1	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	14	0
Non-accrual loans	8	0
Installment and Other Loans [Member ] | Financial Asset, Not Past Due [Member]
Loans	$ 4,675	$ 4,284