Note 2 - Investment Securities - Available-for-sale Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
Securities available-for-sale, amortized cost	$ 1,140,571	$ 1,114,961
Securities available-for-sale, unrealized gains	137	144
Securities available-for-sale, unrealized losses	(106,469)	(124,991)
Securities available-for-sale, fair value	1,034,239	990,114
US Treasury Securities and US Government Agencies Debt Securities [Member]
Securities available-for-sale, amortized cost	247,835	198,182
Securities available-for-sale, unrealized gains	0	33
Securities available-for-sale, unrealized losses	(14)	0
Securities available-for-sale, fair value	247,821	198,215
US Government-sponsored Enterprises Debt Securities [Member]
Securities available-for-sale, amortized cost	86,596	88,895
Securities available-for-sale, unrealized gains	111	110
Securities available-for-sale, unrealized losses	(3,810)	(4,847)
Securities available-for-sale, fair value	82,897	84,158
Mortgage-Backed Security, Issued by US Government-Sponsored Enterprise [Member]
Securities available-for-sale, amortized cost	677,301	696,767
Securities available-for-sale, unrealized gains	24	0
Securities available-for-sale, unrealized losses	(89,358)	(105,790)
Securities available-for-sale, fair value	587,967	590,977
US States and Political Subdivisions Debt Securities [Member]
Securities available-for-sale, amortized cost	126,185	128,431
Securities available-for-sale, unrealized gains	2	1
Securities available-for-sale, unrealized losses	(13,185)	(14,198)
Securities available-for-sale, fair value	113,002	114,234
Other Debt Obligations [Member]
Securities available-for-sale, amortized cost	2,654	2,686
Securities available-for-sale, unrealized gains	0	0
Securities available-for-sale, unrealized losses	(102)	(156)
Securities available-for-sale, fair value	$ 2,552	$ 2,530