Note 6 - Debt Securities in a Continuous Unrealized Loss Position (Details) $ in Thousands	Mar. 31, 2023 USD ($) Security	Dec. 31, 2022 USD ($) Security
Schedule Of Available For Sale Securities [Line Items]
No. of debt securities | Security	561	592
Debt Securities in an unrealized loss position less than 12 months, fair value	$ 20,452	$ 154,673
Debt Securities in an unrealized loss position less than 12 months, unrealized losses	(1,143)	(19,245)
Debt Securities in an unrealized loss position 12 months or longer, fair value	517,452	391,551
Debt Securities in an unrealized loss position 12 months or longer, unrealized losses	(90,140)	(83,449)
Debt Securities in an unrealized loss position, fair value	537,904	546,224
Debt Securities in an unrealized loss position, unrealized losses	$ (91,283)	$ (102,694)
US Government Agencies Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
No. of debt securities | Security	46	46
Debt Securities in an unrealized loss position less than 12 months, fair value		$ 3,647
Debt Securities in an unrealized loss position less than 12 months, unrealized losses		(353)
Debt Securities in an unrealized loss position 12 months or longer, fair value	$ 88,701	83,062
Debt Securities in an unrealized loss position 12 months or longer, unrealized losses	(13,243)	(14,880)
Debt Securities in an unrealized loss position, fair value	88,701	86,709
Debt Securities in an unrealized loss position, unrealized losses	$ (13,243)	$ (15,233)
US States and Political Subdivisions Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
No. of debt securities | Security	192	216
Debt Securities in an unrealized loss position less than 12 months, fair value	$ 4,746	$ 50,156
Debt Securities in an unrealized loss position less than 12 months, unrealized losses	(223)	(7,816)
Debt Securities in an unrealized loss position 12 months or longer, fair value	85,171	45,210
Debt Securities in an unrealized loss position 12 months or longer, unrealized losses	(19,291)	(15,678)
Debt Securities in an unrealized loss position, fair value	89,917	95,366
Debt Securities in an unrealized loss position, unrealized losses	$ (19,514)	$ (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	191	197
Debt Securities in an unrealized loss position less than 12 months, fair value	$ 4,584	$ 58,811
Debt Securities in an unrealized loss position less than 12 months, unrealized losses	(295)	(6,775)
Debt Securities in an unrealized loss position 12 months or longer, fair value	248,400	197,351
Debt Securities in an unrealized loss position 12 months or longer, unrealized losses	(41,019)	(38,528)
Debt Securities in an unrealized loss position, fair value	252,984	256,162
Debt Securities in an unrealized loss position, unrealized losses	$ (41,314)	$ (45,303)
Collateralized Mortgage Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
No. of debt securities | Security	128	129
Debt Securities in an unrealized loss position less than 12 months, fair value	$ 8,213	$ 35,797
Debt Securities in an unrealized loss position less than 12 months, unrealized losses	(534)	(3,983)
Debt Securities in an unrealized loss position 12 months or longer, fair value	91,870	65,875
Debt Securities in an unrealized loss position 12 months or longer, unrealized losses	(16,266)	(14,355)
Debt Securities in an unrealized loss position, fair value	100,083	101,672
Debt Securities in an unrealized loss position, unrealized losses	$ (16,800)	$ (18,338)
Corporate Debt Securities [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	$ 2,909	$ 6,262
Debt Securities in an unrealized loss position less than 12 months, unrealized losses	(91)	(318)
Debt Securities in an unrealized loss position 12 months or longer, fair value	3,310	53
Debt Securities in an unrealized loss position 12 months or longer, unrealized losses	(321)	(8)
Debt Securities in an unrealized loss position, fair value	6,219	6,315
Debt Securities in an unrealized loss position, unrealized losses	$ (412)	$ (326)