Note 3 - Securities - Securities in a Continuous Loss Position (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Temporarily impaired securities, less than 12 months, fair value	$ 31,829	$ 389,208
Temporarily impaired securities, less than 12 months unrealized loss	1,232	39,109
Temporarily impaired securities, 12 months or more fair value	582,007	259,070
Temporarily impaired securities, 12 months or more unrealized loss	89,779	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	940	0
Temporarily impaired securities, 12 months or more unrealized loss	54	0
US Government Agencies Debt Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	24,782	144,574
Temporarily impaired securities, less than 12 months unrealized loss	1,131	12,699
Temporarily impaired securities, 12 months or more fair value	280,119	190,950
Temporarily impaired securities, 12 months or more unrealized loss	47,756	42,303
US States and Political Subdivisions Debt Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	2,070	94,657
Temporarily impaired securities, less than 12 months unrealized loss	35	18,373
Temporarily impaired securities, 12 months or more fair value	144,831	52,134
Temporarily impaired securities, 12 months or more unrealized loss	32,708	19,645
Commercial Mortgage-Backed Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	4,977	144,198
Temporarily impaired securities, less than 12 months unrealized loss	66	7,326
Temporarily impaired securities, 12 months or more fair value	150,514	15,165
Temporarily impaired securities, 12 months or more unrealized loss	8,361	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	5,603	821
Temporarily impaired securities, 12 months or more unrealized loss	$ 900	$ 182