Note 4 - Debt Securities in a Continuous Unrealized Loss Position (Details) $ in Thousands	Dec. 31, 2023 USD ($) Security	Dec. 31, 2022 USD ($) Security
Schedule Of Available For Sale Securities [Line Items]
No. of debt securities | Security	526	592
Debt Securities in an unrealized loss position less than 12 months, fair value	$ 875	$ 154,673
Debt Securities in an unrealized loss position less than 12 months, unrealized losses	0	(19,245)
Debt Securities in an unrealized loss position 12 months or longer, fair value	484,934	391,551
Debt Securities in an unrealized loss position 12 months or longer, unrealized losses	(84,252)	(83,449)
Debt Securities in an unrealized loss position, fair value	485,809	546,224
Debt Securities in an unrealized loss position, unrealized losses	$ (84,252)	$ (102,694)
US Treasury Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
No. of debt securities | Security	1
Debt Securities in an unrealized loss position less than 12 months, fair value	$ 494
Debt Securities in an unrealized loss position less than 12 months, unrealized losses	0
Debt Securities in an unrealized loss position 12 months or longer, fair value	0
Debt Securities in an unrealized loss position 12 months or longer, unrealized losses	0
Debt Securities in an unrealized loss position, fair value	494
Debt Securities in an unrealized loss position, unrealized losses	$ 0
US Government Agencies Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
No. of debt securities | Security	39	46
Debt Securities in an unrealized loss position less than 12 months, fair value	$ 0	$ 3,647
Debt Securities in an unrealized loss position less than 12 months, unrealized losses	0	(353)
Debt Securities in an unrealized loss position 12 months or longer, fair value	74,122	83,062
Debt Securities in an unrealized loss position 12 months or longer, unrealized losses	(10,828)	(14,880)
Debt Securities in an unrealized loss position, fair value	74,122	86,709
Debt Securities in an unrealized loss position, unrealized losses	$ (10,828)	$ (15,233)
US States and Political Subdivisions Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
No. of debt securities | Security	191	216
Debt Securities in an unrealized loss position less than 12 months, fair value	$ 380	$ 50,156
Debt Securities in an unrealized loss position less than 12 months, unrealized losses	0	(7,816)
Debt Securities in an unrealized loss position 12 months or longer, fair value	89,238	45,210
Debt Securities in an unrealized loss position 12 months or longer, unrealized losses	(18,714)	(15,678)
Debt Securities in an unrealized loss position, fair value	89,618	95,366
Debt Securities in an unrealized loss position, unrealized losses	$ (18,714)	$ (23,494)
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule Of Available For Sale Securities [Line Items]
No. of debt securities | Security	165	197
Debt Securities in an unrealized loss position less than 12 months, fair value	$ 1	$ 58,811
Debt Securities in an unrealized loss position less than 12 months, unrealized losses	0	(6,775)
Debt Securities in an unrealized loss position 12 months or longer, fair value	225,500	197,351
Debt Securities in an unrealized loss position 12 months or longer, unrealized losses	(37,831)	(38,528)
Debt Securities in an unrealized loss position, fair value	225,501	256,162
Debt Securities in an unrealized loss position, unrealized losses	$ (37,831)	$ (45,303)
Collateralized Mortgage Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
No. of debt securities | Security	126	129
Debt Securities in an unrealized loss position less than 12 months, fair value	$ 0	$ 35,797
Debt Securities in an unrealized loss position less than 12 months, unrealized losses	0	(3,983)
Debt Securities in an unrealized loss position 12 months or longer, fair value	89,973	65,875
Debt Securities in an unrealized loss position 12 months or longer, unrealized losses	(16,383)	(14,355)
Debt Securities in an unrealized loss position, fair value	89,973	101,672
Debt Securities in an unrealized loss position, unrealized losses	$ (16,383)	$ (18,338)
Corporate Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
No. of debt securities | Security		4
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)
Debt Securities in an unrealized loss position 12 months or longer, fair value		53
Debt Securities in an unrealized loss position 12 months or longer, unrealized losses		(8)
Debt Securities in an unrealized loss position, fair value		6,315
Debt Securities in an unrealized loss position, unrealized losses		$ (326)
Corporate Debt Securities and Money Market Funds [Member]
Schedule Of Available For Sale Securities [Line Items]
No. of debt securities | Security	4
Debt Securities in an unrealized loss position less than 12 months, fair value	$ 0
Debt Securities in an unrealized loss position less than 12 months, unrealized losses	0
Debt Securities in an unrealized loss position 12 months or longer, fair value	6,101
Debt Securities in an unrealized loss position 12 months or longer, unrealized losses	(496)
Debt Securities in an unrealized loss position, fair value	6,101
Debt Securities in an unrealized loss position, unrealized losses	$ (496)