Note 6 - Debt Securities in a Continuous Unrealized Loss Position (Details) $ in Thousands	Mar. 31, 2024 USD ($) Security	Dec. 31, 2023 USD ($) Security
Schedule Of Available For Sale Securities [Line Items]
No. of debt securities | Security	528	526
Debt Securities in an unrealized loss position less than 12 months, fair value	$ 2,970	$ 875
Debt Securities in an unrealized loss position less than 12 months, unrealized losses	(1)	0
Debt Securities in an unrealized loss position 12 months or longer, fair value	471,289	484,934
Debt Securities in an unrealized loss position 12 months or longer, unrealized losses	(88,722)	(84,252)
Debt Securities in an unrealized loss position, fair value	474,259	485,809
Debt Securities in an unrealized loss position, unrealized losses	$ (88,723)	$ (84,252)
US Treasury Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
No. of debt securities | Security	6	1
Debt Securities in an unrealized loss position less than 12 months, fair value	$ 2,970	$ 494
Debt Securities in an unrealized loss position less than 12 months, unrealized losses	(1)	0
Debt Securities in an unrealized loss position 12 months or longer, fair value	0	0
Debt Securities in an unrealized loss position 12 months or longer, unrealized losses	0	0
Debt Securities in an unrealized loss position, fair value	2,970	494
Debt Securities in an unrealized loss position, unrealized losses	$ (1)	$ 0
US Government Agencies Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
No. of debt securities | Security	39	39
Debt Securities in an unrealized loss position less than 12 months, fair value	$ 0	$ 0
Debt Securities in an unrealized loss position less than 12 months, unrealized losses	0	0
Debt Securities in an unrealized loss position 12 months or longer, fair value	73,529	74,122
Debt Securities in an unrealized loss position 12 months or longer, unrealized losses	(11,423)	(10,828)
Debt Securities in an unrealized loss position, fair value	73,529	74,122
Debt Securities in an unrealized loss position, unrealized losses	$ (11,423)	$ (10,828)
US States and Political Subdivisions Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
No. of debt securities | Security	190	191
Debt Securities in an unrealized loss position less than 12 months, fair value	$ 0	$ 380
Debt Securities in an unrealized loss position less than 12 months, unrealized losses	0	0
Debt Securities in an unrealized loss position 12 months or longer, fair value	87,967	89,238
Debt Securities in an unrealized loss position 12 months or longer, unrealized losses	(19,816)	(18,714)
Debt Securities in an unrealized loss position, fair value	87,967	89,618
Debt Securities in an unrealized loss position, unrealized losses	$ (19,816)	$ (18,714)
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule Of Available For Sale Securities [Line Items]
No. of debt securities | Security	164	165
Debt Securities in an unrealized loss position less than 12 months, fair value	$ 0	$ 1
Debt Securities in an unrealized loss position less than 12 months, unrealized losses	0	0
Debt Securities in an unrealized loss position 12 months or longer, fair value	217,140	225,500
Debt Securities in an unrealized loss position 12 months or longer, unrealized losses	(40,093)	(37,831)
Debt Securities in an unrealized loss position, fair value	217,140	225,501
Debt Securities in an unrealized loss position, unrealized losses	$ (40,093)	$ (37,831)
Collateralized Mortgage Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
No. of debt securities | Security	125	126
Debt Securities in an unrealized loss position less than 12 months, fair value	$ 0	$ 0
Debt Securities in an unrealized loss position less than 12 months, unrealized losses	0	0
Debt Securities in an unrealized loss position 12 months or longer, fair value	86,564	89,973
Debt Securities in an unrealized loss position 12 months or longer, unrealized losses	(16,893)	(16,383)
Debt Securities in an unrealized loss position, fair value	86,564	89,973
Debt Securities in an unrealized loss position, unrealized losses	$ (16,893)	$ (16,383)
Corporate Debt Securities and Money Market Funds [Member]
Schedule Of Available For Sale Securities [Line Items]
No. of debt securities | Security	4	4
Debt Securities in an unrealized loss position less than 12 months, fair value	$ 0	$ 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	6,089	6,101
Debt Securities in an unrealized loss position 12 months or longer, unrealized losses	(497)	(496)
Debt Securities in an unrealized loss position, fair value	6,089	6,101
Debt Securities in an unrealized loss position, unrealized losses	$ (497)	$ (496)