Note 5 - Loans - Aging of Loan Portfolio (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Loans	$ 19,548,140	$ 18,254,024
Non-accrual loans	66,681	68,854
Financial Asset, 30 to 59 Days Past Due [Member]
Loans	124,698	81,012
Financial Asset, 60 to 89 Days Past Due [Member]
Loans	38,941	8,921
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Loans	7,157	11,580
Financial Asset, Past Due [Member]
Loans	237,477	170,367
Non-accrual loans	66,681	68,854
Financial Asset, Not Past Due [Member]
Loans	19,310,663	18,083,657
Commercial Portfolio Segment [Member]
Loans	3,305,048	3,318,778
Commercial Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Loans	11,771	8,192
Commercial Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Loans	7,770	3,235
Commercial Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Loans	508	10,208
Commercial Portfolio Segment [Member] | Financial Asset, Past Due [Member]
Loans	34,453	47,407
Non-accrual loans	14,404	25,772
Commercial Portfolio Segment [Member] | Financial Asset, Not Past Due [Member]
Loans	3,270,595	3,271,371
Real Estate Construction Portfolio Segment [Member]
Loans	422,647	559,372
Real Estate Construction Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Loans	25,389	0
Real Estate Construction Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Loans	22,998	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	56,123	0
Non-accrual loans	7,736	0
Real Estate Construction Portfolio Segment [Member] | Financial Asset, Not Past Due [Member]
Loans	366,524	559,372
Commercial Real Estate Portfolio Segment [Member]
Loans	9,729,581	8,793,685
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Loans	27,900	25,772
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Loans	1,503	0
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Loans	6,649	1,372
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, Past Due [Member]
Loans	68,082	61,240
Non-accrual loans	32,030	34,096
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, Not Past Due [Member]
Loans	9,661,499	8,732,445
Residential Mortgage and Equity Lines Portfolio Segment [Member]
Loans	6,084,666	5,577,500
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Loans	59,606	47,043
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Loans	6,670	5,685
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	78,787	61,706
Non-accrual loans	12,511	8,978
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Financial Asset, Not Past Due [Member]
Loans	6,005,879	5,515,794
Installment and Other Loans [Member ]
Loans	6,198	4,689
Installment and Other Loans [Member ] | Financial Asset, 30 to 59 Days Past Due [Member]
Loans	32	5
Installment and Other Loans [Member ] | Financial Asset, 60 to 89 Days Past Due [Member]
Loans	0	1
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	32	14
Non-accrual loans	0	8
Installment and Other Loans [Member ] | Financial Asset, Not Past Due [Member]
Loans	$ 6,166	$ 4,675