Note 3 - Securities - Securities in a Continuous Loss Position (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Temporarily impaired securities, less than 12 months, fair value	$ 2,509	$ 389,208
Temporarily impaired securities, less than 12 months unrealized loss	80	39,109
Temporarily impaired securities, 12 months or more fair value	588,798	259,070
Temporarily impaired securities, 12 months or more unrealized loss	110,451	64,043
US Treasury Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	0	936
Temporarily impaired securities, less than 12 months unrealized loss	0	56
Temporarily impaired securities, 12 months or more fair value	948	0
Temporarily impaired securities, 12 months or more unrealized loss	47	0
US Government Agencies Debt Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	0	144,574
Temporarily impaired securities, less than 12 months unrealized loss	0	12,699
Temporarily impaired securities, 12 months or more fair value	295,989	190,950
Temporarily impaired securities, 12 months or more unrealized loss	57,856	42,303
US States and Political Subdivisions Debt Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	845	94,657
Temporarily impaired securities, less than 12 months unrealized loss	41	18,373
Temporarily impaired securities, 12 months or more fair value	135,979	52,134
Temporarily impaired securities, 12 months or more unrealized loss	42,562	19,645
Commercial Mortgage-Backed Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	1,664	144,198
Temporarily impaired securities, less than 12 months unrealized loss	39	7,326
Temporarily impaired securities, 12 months or more fair value	150,448	15,165
Temporarily impaired securities, 12 months or more unrealized loss	8,916	1,913
Corporate Debt Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	0	4,843
Temporarily impaired securities, less than 12 months unrealized loss	0	655
Temporarily impaired securities, 12 months or more fair value	5,434	821
Temporarily impaired securities, 12 months or more unrealized loss	$ 1,070	$ 182

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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