Note 3 - Investment Securities - Securities in an Unrealized Loss Position (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Temporarily impaired securities, fair value	$ 613,871	$ 374,015
Temporarily impaired securities, unrealized losses	(95,149)	(4,956)
Temporarily impaired securities, fair value, less than 12 months	425,265	338,632
Temporarily impaired securities, unrealized losses, less than 12 months	(50,668)	(3,795)
Temporarily impaired securities, fair value, 12 months or longer	188,606	35,383
Temporarily impaired securities, unrealized losses, 12 months or longer	(44,481)	(1,161)
US Government Agencies Debt Securities [Member]
Temporarily impaired securities, fair value	45,620	28,974
Temporarily impaired securities, unrealized losses	(10,276)	(625)
Temporarily impaired securities, fair value, less than 12 months	30,535	28,974
Temporarily impaired securities, unrealized losses, less than 12 months	(4,261)	(625)
Temporarily impaired securities, fair value, 12 months or longer	15,085	0
Temporarily impaired securities, unrealized losses, 12 months or longer	(6,015)	0
Residential Mortgage-Backed Securities [Member]
Temporarily impaired securities, fair value	406,984	246,396
Temporarily impaired securities, unrealized losses	(61,798)	(2,884)
Temporarily impaired securities, fair value, less than 12 months	293,070	214,701
Temporarily impaired securities, unrealized losses, less than 12 months	(32,342)	(2,111)
Temporarily impaired securities, fair value, 12 months or longer	113,914	31,695
Temporarily impaired securities, unrealized losses, 12 months or longer	(29,456)	(773)
Commercial Mortgage-Backed Securities [Member]
Temporarily impaired securities, fair value	20,895	8,370
Temporarily impaired securities, unrealized losses	(4,651)	(463)
Temporarily impaired securities, fair value, less than 12 months	15,961	4,682
Temporarily impaired securities, unrealized losses, less than 12 months	(2,943)	(75)
Temporarily impaired securities, fair value, 12 months or longer	4,934	3,688
Temporarily impaired securities, unrealized losses, 12 months or longer	(1,708)	(388)
US States and Political Subdivisions Debt Securities [Member]
Temporarily impaired securities, fair value	135,483	89,473
Temporarily impaired securities, unrealized losses	(18,380)	(982)
Temporarily impaired securities, fair value, less than 12 months	81,466	89,473
Temporarily impaired securities, unrealized losses, less than 12 months	(11,098)	(982)
Temporarily impaired securities, fair value, 12 months or longer	54,017	0
Temporarily impaired securities, unrealized losses, 12 months or longer	(7,282)	0
Corporate Debt Securities [Member]
Temporarily impaired securities, fair value	2,991
Temporarily impaired securities, unrealized losses	(8)
Temporarily impaired securities, fair value, less than 12 months	2,991
Temporarily impaired securities, unrealized losses, less than 12 months	(8)
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	1,898	802
Temporarily impaired securities, unrealized losses	(36)	(2)
Temporarily impaired securities, fair value, less than 12 months	1,242	802
Temporarily impaired securities, unrealized losses, less than 12 months	(16)	(2)
Temporarily impaired securities, fair value, 12 months or longer	656	0
Temporarily impaired securities, unrealized losses, 12 months or longer	$ (20)	$ 0