Note 7 - Investment Securities - Temporarily Impaired Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Temporarily impaired securities, less than 12 months, fair value	$ 500,758	$ 137,572
Temporarily impaired securities, less than 12 months, unrealized losses	6,995	423
Temporarily impaired securities, 12 months or longer, fair value	29,301	48,295
Temporarily impaired securities, 12 months or longer, fair value	1,127	1,036
Temporarily impaired securities, total fair value	530,059	185,867
Temporarily impaired securities, total unrealized losses	8,122	1,459
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	2,403	40,009
Temporarily impaired securities, 12 months or longer, fair value	135	444
Temporarily impaired securities, total fair value	2,403	66,399
Temporarily impaired securities, total unrealized losses	135	546
US Treasury Securities [Member]
Temporarily impaired securities, less than 12 months, fair value		40,952
Temporarily impaired securities, less than 12 months, unrealized losses		6
Temporarily impaired securities, 12 months or longer, fair value		0
Temporarily impaired securities, 12 months or longer, fair value		0
Temporarily impaired securities, total fair value		40,952
Temporarily impaired securities, total unrealized losses		6
Collateralized Mortgage Backed Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	399,470	1,694
Temporarily impaired securities, less than 12 months, unrealized losses	5,632	23
Temporarily impaired securities, 12 months or longer, fair value	7,038	8,093
Temporarily impaired securities, 12 months or longer, fair value	696	583
Temporarily impaired securities, total fair value	406,508	9,787
Temporarily impaired securities, total unrealized losses	6,328	606
Collateralized Mortgage Obligations [Member]
Temporarily impaired securities, less than 12 months, fair value	9,418	10,131
Temporarily impaired securities, less than 12 months, unrealized losses	219	25
Temporarily impaired securities, 12 months or longer, fair value	144	193
Temporarily impaired securities, 12 months or longer, fair value	12	9
Temporarily impaired securities, total fair value	9,562	10,324
Temporarily impaired securities, total unrealized losses	231	34
Corporate Debt Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	91,870	58,405
Temporarily impaired securities, less than 12 months, unrealized losses	1,144	267
Temporarily impaired securities, 12 months or longer, fair value	19,716	0
Temporarily impaired securities, 12 months or longer, fair value	284	0
Temporarily impaired securities, total fair value	111,586	58,405
Temporarily impaired securities, total unrealized losses	$ 1,428	$ 267

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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