Note 8 - Investment Securities - Investment Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Investment securities available for sale, amortized cost	$ 1,284,863	$ 1,126,867
Investment securities available for sale, gross unrealized gains	1,625	11,075
Investment securities available for sale, gross unrealized losses	66,947	10,633
Securities available-for-sale	1,219,541	1,127,309
US Treasury Securities [Member]
Investment securities available for sale, amortized cost	119,757
Investment securities available for sale, gross unrealized gains	4
Investment securities available for sale, gross unrealized losses	13
Securities available-for-sale	119,748
US Government Corporations and Agencies Securities [Member]
Investment securities available for sale, amortized cost	82,300	86,475
Investment securities available for sale, gross unrealized gains	1,050	1,169
Investment securities available for sale, gross unrealized losses	134	135
Securities available-for-sale	83,216	87,509
Collateralized Mortgage-Backed Securities [Member]
Investment securities available for sale, amortized cost	929,428	886,614
Investment securities available for sale, gross unrealized gains	521	9,465
Investment securities available for sale, gross unrealized losses	56,444	7,414
Securities available-for-sale	873,505	888,665
Collateralized Mortgage Obligations [Member]
Investment securities available for sale, amortized cost	9,282	9,547
Investment securities available for sale, gross unrealized gains	0	0
Investment securities available for sale, gross unrealized losses	894	430
Securities available-for-sale	8,388	9,117
Corporate Debt Securities [Member]
Investment securities available for sale, amortized cost	144,096	144,231
Investment securities available for sale, gross unrealized gains	50	441
Investment securities available for sale, gross unrealized losses	9,462	2,654
Securities available-for-sale	$ 134,684	$ 142,018