Note 2 - Investment Securities - Held to Maturity Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Securities held-to-maturity, carrying value	$ 445,205	$ 473,217
Securities held-to-maturity, gains	0	0
Securities held-to-maturity, losses	(47,787)	(41,384)
Securities held-to-maturity, fair value	397,418	431,833
US Treasury Securities and US Government Agencies Debt Securities [Member]
Securities held-to-maturity, carrying value	204,139	217,794
Securities held-to-maturity, gains	0	0
Securities held-to-maturity, losses	(7,645)	(9,166)
Securities held-to-maturity, fair value	196,494	208,628
US Government-sponsored Enterprises Debt Securities [Member]
Securities held-to-maturity, carrying value	26,972	27,507
Securities held-to-maturity, gains	0	0
Securities held-to-maturity, losses	(3,536)	(2,559)
Securities held-to-maturity, fair value	23,436	24,948
Mortgage-Backed Securities, Issued by US Government Sponsored Enterprises [Member]
Securities held-to-maturity, carrying value	214,094	227,916
Securities held-to-maturity, gains	0	0
Securities held-to-maturity, losses	(36,606)	(29,659)
Securities held-to-maturity, fair value	$ 177,488	$ 198,257

Amount, before allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity).

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Amount of accumulated unrecognized gain on investment in debt security measured at amortized cost (held-to-maturity).

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