Note 3 - Investment Securities - Temporarily Impaired Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Temporarily impaired securities, less than 12 months, fair value	$ 639,985	$ 137,572
Temporarily impaired securities, less than 12 months, unrealized losses	9,198	423
Temporarily impaired securities, 12 months or longer, fair value	28,429	48,295
Temporarily impaired securities, 12 months or longer, unrealized losses	1,435	1,036
Temporarily impaired securities, total fair value	668,414	185,867
Temporarily impaired securities, total unrealized losses	10,633	1,459
US Treasury Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	0	40,952
Temporarily impaired securities, less than 12 months, unrealized losses	0	6
Temporarily impaired securities, 12 months or longer, fair value	0	0
Temporarily impaired securities, 12 months or longer, unrealized losses	0	0
Temporarily impaired securities, total fair value	0	40,952
Temporarily impaired securities, total unrealized losses	0	6
US Government Corporations and Agencies Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	0	26,390
Temporarily impaired securities, less than 12 months, unrealized losses	0	102
Temporarily impaired securities, 12 months or longer, fair value	2,337	40,009
Temporarily impaired securities, 12 months or longer, unrealized losses	135	444
Temporarily impaired securities, total fair value	2,337	66,399
Temporarily impaired securities, total unrealized losses	135	546
Collateralized Mortgage Backed Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	527,276	1,694
Temporarily impaired securities, less than 12 months, unrealized losses	6,659	23
Temporarily impaired securities, 12 months or longer, fair value	6,496	8,093
Temporarily impaired securities, 12 months or longer, unrealized losses	755	583
Temporarily impaired securities, total fair value	533,772	9,787
Temporarily impaired securities, total unrealized losses	7,414	606
Collateralized Mortgage Obligations [Member]
Temporarily impaired securities, less than 12 months, fair value	8,989	10,131
Temporarily impaired securities, less than 12 months, unrealized losses	417	25
Temporarily impaired securities, 12 months or longer, fair value	128	193
Temporarily impaired securities, 12 months or longer, unrealized losses	13	9
Temporarily impaired securities, total fair value	9,117	10,324
Temporarily impaired securities, total unrealized losses	430	34
Corporate Debt Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	103,720	58,405
Temporarily impaired securities, less than 12 months, unrealized losses	2,122	267
Temporarily impaired securities, 12 months or longer, fair value	19,468	0
Temporarily impaired securities, 12 months or longer, unrealized losses	532	0
Temporarily impaired securities, total fair value	123,188	58,405
Temporarily impaired securities, total unrealized losses	$ 2,654	$ 267