Note 4 - Investment Securities - Summary of Amortized Cost and Fair Value of Investment Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Held-to-maturity securities (fair value of $193,627 in 2024; $197,176 in 2023)	$ 224,989	$ 224,233
Held to maturity securities, gross unrealized gains	0	0
Held to maturity securities, gross unrealized losses	(31,362)	(27,057)
Held to maturity securities, fair value	193,627	197,176
Available for sale securities, amortized cost	380,848	395,635
Available for sale debt securities, gross unrealized gains	0	1
Available for sale securities, gross unrealized losses	(53,342)	(51,596)
Available for sale debt security, fair value	327,506	344,040
US Government Agencies Debt Securities [Member]
Held-to-maturity securities (fair value of $193,627 in 2024; $197,176 in 2023)	81,928	81,382
Held to maturity securities, gross unrealized gains	0	0
Held to maturity securities, gross unrealized losses	(8,678)	(7,561)
Held to maturity securities, fair value	73,250	73,821
Available for sale securities, amortized cost	31,225	31,178
Available for sale debt securities, gross unrealized gains	0	0
Available for sale securities, gross unrealized losses	(3,629)	(3,633)
Available for sale debt security, fair value	27,596	27,545
US States and Political Subdivisions Debt Securities [Member]
Held-to-maturity securities (fair value of $193,627 in 2024; $197,176 in 2023)	143,061	142,851
Held to maturity securities, gross unrealized gains	0	0
Held to maturity securities, gross unrealized losses	(22,684)	(19,496)
Held to maturity securities, fair value	120,377	123,355
Available for sale securities, amortized cost	135,688	138,217
Available for sale debt securities, gross unrealized gains	0	1
Available for sale securities, gross unrealized losses	(16,028)	(15,421)
Available for sale debt security, fair value	119,660	122,797
Mortgage-Backed Security, Issued by US Government-Sponsored Enterprise [Member]
Available for sale securities, amortized cost	213,935	226,240
Available for sale debt securities, gross unrealized gains	0	0
Available for sale securities, gross unrealized losses	(33,685)	(32,542)
Available for sale debt security, fair value	$ 180,250	$ 193,698

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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