Note 4 - Debt Securities in a Continuous Unrealized Loss Position (Details) $ in Thousands	Dec. 31, 2021 USD ($) security	Dec. 31, 2020 USD ($) security
Schedule Of Available For Sale Securities [Line Items]
No. of debt securities | security	266	39
Debt Securities in an unrealized loss position less than 12 months, fair value	$ 463,870	$ 59,434
Debt Securities in an unrealized loss position less than 12 months, unrealized losses	(6,923)	(349)
Debt Securities in an unrealized loss position 12 months or longer, fair value	44,154	70
Debt Securities in an unrealized loss position 12 months or longer, unrealized losses	(1,379)	(14)
Debt Securities in an unrealized loss position, fair value	508,024	59,504
Debt Securities in an unrealized loss position, unrealized losses	$ (8,302)	$ (363)
US Government Agencies Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
No. of debt securities | security	44	19
Debt Securities in an unrealized loss position less than 12 months, fair value	$ 62,530	$ 37,754
Debt Securities in an unrealized loss position less than 12 months, unrealized losses	(1,407)	(246)
Debt Securities in an unrealized loss position 12 months or longer, fair value	32,968
Debt Securities in an unrealized loss position 12 months or longer, unrealized losses	(1,028)
Debt Securities in an unrealized loss position, fair value	95,498	37,754
Debt Securities in an unrealized loss position, unrealized losses	$ (2,435)	$ (246)
US States and Political Subdivisions Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
No. of debt securities | security	103	11
Debt Securities in an unrealized loss position less than 12 months, fair value	$ 55,982	$ 6,821
Debt Securities in an unrealized loss position less than 12 months, unrealized losses	(953)	(45)
Debt Securities in an unrealized loss position 12 months or longer, fair value	3,742
Debt Securities in an unrealized loss position 12 months or longer, unrealized losses	(100)
Debt Securities in an unrealized loss position, fair value	59,724	6,821
Debt Securities in an unrealized loss position, unrealized losses	$ (1,053)	$ (45)
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule Of Available For Sale Securities [Line Items]
No. of debt securities | security	72	4
Debt Securities in an unrealized loss position less than 12 months, fair value	$ 253,141	$ 8,626
Debt Securities in an unrealized loss position less than 12 months, unrealized losses	(2,915)	(24)
Debt Securities in an unrealized loss position 12 months or longer, fair value	7,370
Debt Securities in an unrealized loss position 12 months or longer, unrealized losses	(243)
Debt Securities in an unrealized loss position, fair value	260,511	8,626
Debt Securities in an unrealized loss position, unrealized losses	$ (3,158)	$ (24)
Collateralized Mortgage Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
No. of debt securities | security	46	3
Debt Securities in an unrealized loss position less than 12 months, fair value	$ 92,217	$ 3,262
Debt Securities in an unrealized loss position less than 12 months, unrealized losses	(1,648)	(5)
Debt Securities in an unrealized loss position, fair value	92,217	3,262
Debt Securities in an unrealized loss position, unrealized losses	$ (1,648)	$ (5)
Collateralized Debt Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
No. of debt securities | security	1	1
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	75	70
Debt Securities in an unrealized loss position 12 months or longer, unrealized losses	(8)	(14)
Debt Securities in an unrealized loss position, fair value	75	70
Debt Securities in an unrealized loss position, unrealized losses	$ (8)	$ (14)
Corporate Debt 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		$ 2,971
Debt Securities in an unrealized loss position less than 12 months, unrealized losses		(29)
Debt Securities in an unrealized loss position, fair value		2,971
Debt Securities in an unrealized loss position, unrealized losses		$ (29)