Note 3 - Investment Securities - Investment Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Investment securities available for sale, amortized cost	$ 1,126,867	$ 1,019,230
Investment securities available for sale, gross unrealized gains	11,075	18,779
Investment securities available for sale, gross unrealized losses	10,633	1,459
Securities available-for-sale	1,127,309	1,036,550
US Treasury Securities [Member]
Investment securities available for sale, amortized cost	0	80,948
Investment securities available for sale, gross unrealized gains	0	6
Investment securities available for sale, gross unrealized losses	0	6
Securities available-for-sale	0	80,948
US Government Corporations and Agencies Securities [Member]
Investment securities available for sale, amortized cost	86,475	99,944
Investment securities available for sale, gross unrealized gains	1,169	441
Investment securities available for sale, gross unrealized losses	135	546
Securities available-for-sale	87,509	99,839
Collateralized Mortgage Backed Securities [Member]
Investment securities available for sale, amortized cost	886,614	709,709
Investment securities available for sale, gross unrealized gains	9,465	17,965
Investment securities available for sale, gross unrealized losses	7,414	606
Securities available-for-sale	888,665	727,068
Collateralized Mortgage Obligations [Member]
Investment securities available for sale, amortized cost	9,547	10,358
Investment securities available for sale, gross unrealized gains	0	0
Investment securities available for sale, gross unrealized losses	430	34
Securities available-for-sale	9,117	10,324
Corporate Debt Securities [Member]
Investment securities available for sale, amortized cost	144,231	118,271
Investment securities available for sale, gross unrealized gains	441	367
Investment securities available for sale, gross unrealized losses	2,654	267
Securities available-for-sale	$ 142,018	$ 118,371