Note 3 - Investment Securities - Securities in an Unrealized Loss Position (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Temporarily impaired securities, fair value	$ 608,473	$ 374,015
Temporarily impaired securities, unrealized losses	(87,204)	(4,956)
Temporarily impaired securities, fair value, less than 12 months	307,425	338,632
Temporarily impaired securities, unrealized losses, less than 12 months	(21,450)	(3,795)
Temporarily impaired securities, fair value, 12 months or longer	301,048	35,383
Temporarily impaired securities, unrealized losses, 12 months or longer	(65,754)	(1,161)
US Government Agencies Debt Securities [Member]
Temporarily impaired securities, fair value	44,451	28,974
Temporarily impaired securities, unrealized losses	(10,439)	(625)
Temporarily impaired securities, fair value, less than 12 months	20,517	28,974
Temporarily impaired securities, unrealized losses, less than 12 months	(1,831)	(625)
Temporarily impaired securities, fair value, 12 months or longer	23,934	0
Temporarily impaired securities, unrealized losses, 12 months or longer	(8,608)	0
Residential Mortgage-Backed Securities [Member]
Temporarily impaired securities, fair value	403,039	246,396
Temporarily impaired securities, unrealized losses	(57,863)	(2,884)
Temporarily impaired securities, fair value, less than 12 months	218,918	214,701
Temporarily impaired securities, unrealized losses, less than 12 months	(13,869)	(2,111)
Temporarily impaired securities, fair value, 12 months or longer	184,121	31,695
Temporarily impaired securities, unrealized losses, 12 months or longer	(43,994)	(773)
Commercial Mortgage-Backed Securities [Member]
Temporarily impaired securities, fair value	21,105	8,370
Temporarily impaired securities, unrealized losses	(4,381)	(463)
Temporarily impaired securities, fair value, less than 12 months	14,523	4,682
Temporarily impaired securities, unrealized losses, less than 12 months	(2,304)	(75)
Temporarily impaired securities, fair value, 12 months or longer	6,582	3,688
Temporarily impaired securities, unrealized losses, 12 months or longer	(2,077)	(388)
US States and Political Subdivisions Debt Securities [Member]
Temporarily impaired securities, fair value	133,265	89,473
Temporarily impaired securities, unrealized losses	(14,462)	(982)
Temporarily impaired securities, fair value, less than 12 months	47,446	89,473
Temporarily impaired securities, unrealized losses, less than 12 months	(3,404)	(982)
Temporarily impaired securities, fair value, 12 months or longer	85,819	0
Temporarily impaired securities, unrealized losses, 12 months or longer	(11,058)	0
Corporate Debt Securities [Member]
Temporarily impaired securities, fair value	4,973
Temporarily impaired securities, unrealized losses	(26)
Temporarily impaired securities, fair value, less than 12 months	4,973
Temporarily impaired securities, unrealized losses, less than 12 months	(26)
Temporarily impaired securities, fair value, 12 months or longer	0
Temporarily impaired securities, unrealized losses, 12 months or longer	0
Asset-Backed Securities [Member]
Temporarily impaired securities, fair value	1,640	802
Temporarily impaired securities, unrealized losses	(33)	(2)
Temporarily impaired securities, fair value, less than 12 months	1,048	802
Temporarily impaired securities, unrealized losses, less than 12 months	(16)	(2)
Temporarily impaired securities, fair value, 12 months or longer	592	0
Temporarily impaired securities, unrealized losses, 12 months or longer	$ (17)	$ 0