Note 8 - Investment Securities - Temporarily Impaired Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Temporarily impaired securities, less than 12 months, fair value	$ 936,267	$ 639,985
Temporarily impaired securities, less than 12 months, unrealized losses	76,305	9,198
Temporarily impaired securities, 12 months or longer, fair value	410,491	28,429
Temporarily impaired securities, 12 months or longer, unrealized losses	87,179	1,435
Temporarily impaired securities, total fair value	1,346,758	668,414
Temporarily impaired securities, total unrealized losses	163,484	10,633
US Treasury Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	241,400
Temporarily impaired securities, less than 12 months, unrealized losses	1,110
Temporarily impaired securities, 12 months or longer, fair value	0
Temporarily impaired securities, 12 months or longer, unrealized losses	0
Temporarily impaired securities, total fair value	241,400
Temporarily impaired securities, total unrealized losses	1,110
US Government Corporations and Agencies Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	0	0
Temporarily impaired securities, less than 12 months, unrealized losses	0	0
Temporarily impaired securities, 12 months or longer, fair value	2,155	2,337
Temporarily impaired securities, 12 months or longer, unrealized losses	126	135
Temporarily impaired securities, total fair value	2,155	2,337
Temporarily impaired securities, total unrealized losses	126	135
Collateralized Mortgage-Backed Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	551,053	527,276
Temporarily impaired securities, less than 12 months, unrealized losses	69,037	6,659
Temporarily impaired securities, 12 months or longer, fair value	309,737	6,496
Temporarily impaired securities, 12 months or longer, unrealized losses	71,365	755
Temporarily impaired securities, total fair value	860,790	533,772
Temporarily impaired securities, total unrealized losses	140,402	7,414
Collateralized Mortgage Obligations [Member]
Temporarily impaired securities, less than 12 months, fair value	24,901	8,989
Temporarily impaired securities, less than 12 months, unrealized losses	1,794	417
Temporarily impaired securities, 12 months or longer, fair value	6,809	128
Temporarily impaired securities, 12 months or longer, unrealized losses	1,875	13
Temporarily impaired securities, total fair value	31,710	9,117
Temporarily impaired securities, total unrealized losses	3,669	430
Corporate Debt Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	118,913	103,720
Temporarily impaired securities, less than 12 months, unrealized losses	4,364	2,122
Temporarily impaired securities, 12 months or longer, fair value	91,790	19,468
Temporarily impaired securities, 12 months or longer, unrealized losses	13,813	532
Temporarily impaired securities, total fair value	210,703	123,188
Temporarily impaired securities, total unrealized losses	$ 18,177	$ 2,654

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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