Note 4 - Debt Securities in a Continuous Unrealized Loss Position (Details) $ in Thousands	Dec. 31, 2022 USD ($) security	Dec. 31, 2021 USD ($) security
Schedule Of Available For Sale Securities [Line Items]
No. of debt securities | security	592	266
Debt Securities in an unrealized loss position less than 12 months, fair value	$ 154,673	$ 463,870
Debt Securities in an unrealized loss position less than 12 months, unrealized losses	(19,245)	(6,923)
Debt Securities in an unrealized loss position 12 months or longer, fair value	391,551	44,155
Debt Securities in an unrealized loss position 12 months or longer, unrealized losses	(83,449)	(1,379)
Debt Securities in an unrealized loss position, fair value	546,224	508,025
Debt Securities in an unrealized loss position, unrealized losses	$ (102,694)	$ (8,302)
US Government Agencies Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
No. of debt securities | security	46	44
Debt Securities in an unrealized loss position less than 12 months, fair value	$ 3,647	$ 62,530
Debt Securities in an unrealized loss position less than 12 months, unrealized losses	(353)	(1,407)
Debt Securities in an unrealized loss position 12 months or longer, fair value	83,062	32,968
Debt Securities in an unrealized loss position 12 months or longer, unrealized losses	(14,880)	(1,028)
Debt Securities in an unrealized loss position, fair value	86,709	95,498
Debt Securities in an unrealized loss position, unrealized losses	$ (15,233)	$ (2,435)
US States and Political Subdivisions Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
No. of debt securities | security	216	103
Debt Securities in an unrealized loss position less than 12 months, fair value	$ 50,156	$ 55,982
Debt Securities in an unrealized loss position less than 12 months, unrealized losses	(7,816)	(953)
Debt Securities in an unrealized loss position 12 months or longer, fair value	45,210	3,742
Debt Securities in an unrealized loss position 12 months or longer, unrealized losses	(15,678)	(100)
Debt Securities in an unrealized loss position, fair value	95,366	59,724
Debt Securities in an unrealized loss position, unrealized losses	$ (23,494)	$ (1,053)
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule Of Available For Sale Securities [Line Items]
No. of debt securities | security	197	72
Debt Securities in an unrealized loss position less than 12 months, fair value	$ 58,811	$ 253,141
Debt Securities in an unrealized loss position less than 12 months, unrealized losses	(6,775)	(2,915)
Debt Securities in an unrealized loss position 12 months or longer, fair value	197,351	7,370
Debt Securities in an unrealized loss position 12 months or longer, unrealized losses	(38,528)	(243)
Debt Securities in an unrealized loss position, fair value	256,162	260,511
Debt Securities in an unrealized loss position, unrealized losses	$ (45,303)	$ (3,158)
Collateralized Mortgage Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
No. of debt securities | security	129	46
Debt Securities in an unrealized loss position less than 12 months, fair value	$ 35,797	$ 92,217
Debt Securities in an unrealized loss position less than 12 months, unrealized losses	(3,983)	(1,648)
Debt Securities in an unrealized loss position 12 months or longer, fair value	65,875
Debt Securities in an unrealized loss position 12 months or longer, unrealized losses	(14,355)
Debt Securities in an unrealized loss position, fair value	101,672	92,217
Debt Securities in an unrealized loss position, unrealized losses	$ (18,338)	$ (1,648)
Corporate Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
No. of debt securities | security	4	1
Debt Securities in an unrealized loss position less than 12 months, fair value	$ 6,262
Debt Securities in an unrealized loss position less than 12 months, unrealized losses	(318)	$ 0
Debt Securities in an unrealized loss position 12 months or longer, fair value	53	75
Debt Securities in an unrealized loss position 12 months or longer, unrealized losses	(8)	(8)
Debt Securities in an unrealized loss position, fair value	6,315	75
Debt Securities in an unrealized loss position, unrealized losses	$ (326)	$ (8)