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Note 2 - INVESTMENT SECURITIES - Amortized Cost and Fair Value of HTM and AFS Investment Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Securities HTM:
Securities held to maturity, at amortized cost, net of allowance for credit losses	$ 718,623	$ 683,504
Securities HTM, Amortized cost	718,826	683,707
Securities HTM, Allowance for Credit (Losses)	(203)	(203)
Securities HTM, Gross Unrealized Gains	25,468	33,429
Securities HTM, Gross Unrealized (Losses)	(47,921)	(36,654)
Securities HTM, Fair Value	696,170	680,279
Securities AFS:
Securities AFS, Amortized Cost	342,660	348,633
Securities AFS, Allowance for Credit (Losses)		(989)
Securities AFS, Gross Unrealized Gains	222	190
Securities AFS, Gross Unrealized (Losses)	(51,902)	(48,179)
Securities AFS, Fair Value	290,980	299,655
U.S. govt. sponsored agency securities
Securities AFS:
Securities AFS, Amortized Cost	17,054	17,399
Securities AFS, Gross Unrealized Gains	10	12
Securities AFS, Gross Unrealized (Losses)	(2,622)	(2,438)
Securities AFS, Fair Value	14,442	14,973
Residential mortgage-backed and related securities
Securities AFS:
Securities AFS, Amortized Cost	62,350	65,168
Securities AFS, Gross Unrealized (Losses)	(6,279)	(5,972)
Securities AFS, Fair Value	56,071	59,196
Municipal securities.
Securities HTM:
Securities HTM, Amortized cost	717,776	682,657
Securities HTM, Allowance for Credit (Losses)	(202)	(202)	$ (180)	$ (180)
Securities HTM, Gross Unrealized Gains	25,468	33,385
Securities HTM, Gross Unrealized (Losses)	(47,907)	(36,639)
Securities HTM, Fair Value	695,135	679,201
Securities AFS:
Securities AFS, Amortized Cost	205,928	206,566
Securities AFS, Gross Unrealized Gains	3	11
Securities AFS, Gross Unrealized (Losses)	(39,238)	(35,590)
Securities AFS, Fair Value	166,693	170,987
Asset-backed securities
Securities AFS:
Securities AFS, Amortized Cost	14,093	15,261
Securities AFS, Gross Unrealized Gains	194	167
Securities AFS, Gross Unrealized (Losses)	(2)	(5)
Securities AFS, Fair Value	14,285	15,423
Corporate Debt Securities [Member]
Securities AFS:
Securities AFS, Allowance for Credit (Losses)		(989)	$ (989)
Other securities
Securities HTM:
Securities held to maturity, at amortized cost, net of allowance for credit losses	1,050
Securities HTM, Amortized cost		1,050
Securities HTM, Allowance for Credit (Losses)	(1)	(1)
Securities HTM, Gross Unrealized Gains		44
Securities HTM, Gross Unrealized (Losses)	(14)	(15)
Securities HTM, Fair Value	1,035	1,078
Securities AFS:
Securities AFS, Amortized Cost	43,235	44,239
Securities AFS, Allowance for Credit (Losses)		(989)
Securities AFS, Gross Unrealized Gains	15
Securities AFS, Gross Unrealized (Losses)	(3,761)	(4,174)
Securities AFS, Fair Value	$ 39,489	$ 39,076