Note 6 - Debt Securities in a Continuous Unrealized Loss Position (Details) $ in Thousands	Jun. 30, 2021 USD ($) security	Dec. 31, 2020 USD ($) security
Schedule Of Available For Sale Securities [Line Items]
No. of debt securities | security	154	39
Debt Securities in an unrealized loss position less than 12 months, fair value	$ 255,347	$ 59,434
Debt Securities in an unrealized loss position less than 12 months, unrealized losses	(3,062)	(349)
Debt Securities in an unrealized loss position 12 months or longer, fair value	110	70
Debt Securities in an unrealized loss position 12 months or longer, unrealized losses	(12)	(14)
Debt Securities in an unrealized loss position, fair value	255,457	59,504
Debt Securities in an unrealized loss position, unrealized losses	$ (3,074)	$ (363)
US Government Agencies Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
No. of debt securities | security	32	19
Debt Securities in an unrealized loss position less than 12 months, fair value	$ 62,908	$ 37,754
Debt Securities in an unrealized loss position less than 12 months, unrealized losses	(1,084)	(246)
Debt Securities in an unrealized loss position, fair value	62,908	37,754
Debt Securities in an unrealized loss position, unrealized losses	$ (1,084)	$ (246)
US States and Political Subdivisions Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
No. of debt securities | security	70	11
Debt Securities in an unrealized loss position less than 12 months, fair value	$ 44,351	$ 6,821
Debt Securities in an unrealized loss position less than 12 months, unrealized losses	(688)	(45)
Debt Securities in an unrealized loss position, fair value	44,351	6,821
Debt Securities in an unrealized loss position, unrealized losses	$ (688)	$ (45)
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule Of Available For Sale Securities [Line Items]
No. of debt securities | security	37	4
Debt Securities in an unrealized loss position less than 12 months, fair value	$ 121,209	$ 8,626
Debt Securities in an unrealized loss position less than 12 months, unrealized losses	(1,055)	(24)
Debt Securities in an unrealized loss position, fair value	121,209	8,626
Debt Securities in an unrealized loss position, unrealized losses	$ (1,055)	$ (24)
Collateralized Mortgage Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
No. of debt securities | security	14	3
Debt Securities in an unrealized loss position less than 12 months, fair value	$ 26,879	$ 3,262
Debt Securities in an unrealized loss position less than 12 months, unrealized losses	(235)	(5)
Debt Securities in an unrealized loss position 12 months or longer, fair value	38
Debt Securities in an unrealized loss position, fair value	26,917	3,262
Debt Securities in an unrealized loss position, unrealized losses	$ (235)	$ (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 12 months or longer, fair value	$ 72	$ 70
Debt Securities in an unrealized loss position 12 months or longer, unrealized losses	(12)	(14)
Debt Securities in an unrealized loss position, fair value	72	70
Debt Securities in an unrealized loss position, unrealized losses	$ (12)	$ (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)