Note 8 - Investment Securities - Investment Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Investment securities available for sale, amortized cost	$ 1,336,293	$ 1,126,867
Investment securities available for sale, gross unrealized gains	1,393	11,075
Investment securities available for sale, gross unrealized losses	103,115	10,633
Securities available-for-sale	1,234,571	1,127,309
US Treasury Securities [Member]
Investment securities available for sale, amortized cost	119,823
Investment securities available for sale, gross unrealized gains	0
Investment securities available for sale, gross unrealized losses	825
Securities available-for-sale	118,998
US Government Corporations and Agencies Securities [Member]
Investment securities available for sale, amortized cost	75,781	86,475
Investment securities available for sale, gross unrealized gains	1,285	1,169
Investment securities available for sale, gross unrealized losses	125	135
Securities available-for-sale	76,941	87,509
Collateralized Mortgage-Backed Securities [Member]
Investment securities available for sale, amortized cost	932,753	886,614
Investment securities available for sale, gross unrealized gains	108	9,465
Investment securities available for sale, gross unrealized losses	88,398	7,414
Securities available-for-sale	844,463	888,665
Collateralized Mortgage Obligations [Member]
Investment securities available for sale, amortized cost	23,949	9,547
Investment securities available for sale, gross unrealized gains	0	0
Investment securities available for sale, gross unrealized losses	1,369	430
Securities available-for-sale	22,580	9,117
Corporate Debt Securities [Member]
Investment securities available for sale, amortized cost	183,987	144,231
Investment securities available for sale, gross unrealized gains	0	441
Investment securities available for sale, gross unrealized losses	12,398	2,654
Securities available-for-sale	$ 171,589	$ 142,018