Note 3 - Investment Securities - Held to Maturity Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Securities held-to-maturity, carrying value	$ 468,751	$ 473,217
Securities held-to-maturity, gains	0	0
Securities held-to-maturity, losses	(34,851)	(41,384)
Debt Securities, Held-to-Maturity, Fair Value, Total	433,900	431,833
US Treasury Securities and US Government Agencies Debt Securities [Member]
Securities held-to-maturity, carrying value	217,906	217,794
Securities held-to-maturity, gains	0	0
Securities held-to-maturity, losses	(7,065)	(9,166)
Debt Securities, Held-to-Maturity, Fair Value, Total	210,841	208,628
US Government-sponsored Enterprises Debt Securities [Member]
Securities held-to-maturity, carrying value	27,229	27,507
Securities held-to-maturity, gains	0	0
Securities held-to-maturity, losses	(1,884)	(2,559)
Debt Securities, Held-to-Maturity, Fair Value, Total	25,345	24,948
Mortgage-Backed Securities, Issued by US Government Sponsored Enterprises [Member]
Securities held-to-maturity, carrying value	223,616	227,916
Securities held-to-maturity, gains	0	0
Securities held-to-maturity, losses	(25,902)	(29,659)
Debt Securities, Held-to-Maturity, Fair Value, Total	$ 197,714	$ 198,257