Note 4 - Loans - Aging of Loan Portfolio (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Loans	$ 19,375,955	$ 19,548,140
Non-accrual loans	169,161	66,681
Financial Asset, 30 to 59 Days Past Due [Member]
Loans	86,041	124,698
Financial Asset, 60 to 89 Days Past Due [Member]
Loans	20,860	38,941
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Loans	4,050	7,157
Financial Asset, Past Due [Member]
Loans	280,112	237,477
Non-accrual loans	169,161	66,681
Financial Asset, Not Past Due [Member]
Loans	19,095,843	19,310,663
Commercial Portfolio Segment [Member]
Loans	3,098,004	3,305,048
Commercial Portfolio Segment [Member] \| Financial Asset, 30 to 59 Days Past Due [Member]
Loans	25,164	11,771
Commercial Portfolio Segment [Member] \| Financial Asset, 60 to 89 Days Past Due [Member]
Loans	275	7,770
Commercial Portfolio Segment [Member] \| Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Loans	2,590	508
Commercial Portfolio Segment [Member] \| Financial Asset, Past Due [Member]
Loans	87,796	34,453
Non-accrual loans	59,767	14,404
Commercial Portfolio Segment [Member] \| Financial Asset, Not Past Due [Member]
Loans	3,010,208	3,270,595
Real Estate Construction Portfolio Segment [Member]
Loans	319,649	422,647
Real Estate Construction Portfolio Segment [Member] \| Financial Asset, 30 to 59 Days Past Due [Member]
Loans	5,334	25,389
Real Estate Construction Portfolio Segment [Member] \| Financial Asset, 60 to 89 Days Past Due [Member]
Loans	0	22,998
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	5,334	56,123
Non-accrual loans	0	7,736
Real Estate Construction Portfolio Segment [Member] \| Financial Asset, Not Past Due [Member]
Loans	314,315	366,524
Commercial Real Estate Portfolio Segment [Member]
Loans	10,033,830	9,729,581
Commercial Real Estate Portfolio Segment [Member] \| Financial Asset, 30 to 59 Days Past Due [Member]
Loans	16,525	27,900
Commercial Real Estate Portfolio Segment [Member] \| Financial Asset, 60 to 89 Days Past Due [Member]
Loans	13,934	1,503
Commercial Real Estate Portfolio Segment [Member] \| Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Loans	1,460	6,649
Commercial Real Estate Portfolio Segment [Member] \| Financial Asset, Past Due [Member]
Loans	115,047	68,082
Non-accrual loans	83,128	32,030
Commercial Real Estate Portfolio Segment [Member] \| Financial Asset, Not Past Due [Member]
Loans	9,918,783	9,661,499
Residential Mortgage and Equity Lines Portfolio Segment [Member]
Loans	5,919,092	6,084,666
Residential Mortgage and Equity Lines Portfolio Segment [Member] \| Financial Asset, 30 to 59 Days Past Due [Member]
Loans	39,018	59,606
Residential Mortgage and Equity Lines Portfolio Segment [Member] \| Financial Asset, 60 to 89 Days Past Due [Member]
Loans	6,651	6,670
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	71,935	78,787
Non-accrual loans	26,266	12,511
Residential Mortgage and Equity Lines Portfolio Segment [Member] \| Financial Asset, Not Past Due [Member]
Loans	5,847,157	6,005,879
Installment and Other Loans [Member ]
Loans	5,380	6,198
Installment and Other Loans [Member ] \| Financial Asset, 30 to 59 Days Past Due [Member]
Loans	0	32
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	0	32
Non-accrual loans	0	0
Installment and Other Loans [Member ] \| Financial Asset, Not Past Due [Member]
Loans	$ 5,380	$ 6,166