Note 4 - Investment Securities - Investment Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Investment securities available for sale, amortized cost	$ 1,622,173	$ 1,126,867
Investment securities available for sale, gross unrealized gains	690	11,075
Investment securities available for sale, gross unrealized losses	149,515	10,633
Securities available-for-sale	1,473,348	1,127,309
US Treasury Securities [Member]
Investment securities available for sale, amortized cost	241,611	0
Investment securities available for sale, gross unrealized gains	0	0
Investment securities available for sale, gross unrealized losses	1,111	0
Securities available-for-sale	240,500	0
US Government Corporations and Agencies Securities [Member]
Investment securities available for sale, amortized cost	63,347	86,475
Investment securities available for sale, gross unrealized gains	384	1,169
Investment securities available for sale, gross unrealized losses	121	135
Securities available-for-sale	63,610	87,509
US Government-sponsored Enterprises Debt Securities [Member]
Investment securities available for sale, amortized cost	30,000
Investment securities available for sale, gross unrealized gains	0
Investment securities available for sale, gross unrealized losses	0
Securities available-for-sale	30,000
Collateralized Mortgage-Backed Securities [Member]
Investment securities available for sale, amortized cost	993,883	886,614
Investment securities available for sale, gross unrealized gains	194	9,465
Investment securities available for sale, gross unrealized losses	126,983	7,414
Securities available-for-sale	867,094	888,665
Collateralized Mortgage Obligations [Member]
Investment securities available for sale, amortized cost	34,552	9,547
Investment securities available for sale, gross unrealized gains	0	0
Investment securities available for sale, gross unrealized losses	3,491	430
Securities available-for-sale	31,061	9,117
Corporate Debt Securities [Member]
Investment securities available for sale, amortized cost	258,780	144,231
Investment securities available for sale, gross unrealized gains	112	441
Investment securities available for sale, gross unrealized losses	17,809	2,654
Securities available-for-sale	$ 241,083	$ 142,018

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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