Note 2 - Investment Securities (Tables)

12 Months Ended

Dec. 31, 2023

Notes Tables

Debt Securities, Available-for-sale and Held-to-maturity [Table Text Block]

	At December 31, 2023
			Gross		Gross
	Amortized		Unrealized		Unrealized			Fair
	Cost		Gains		Losses			Value
	(In thousands)
Debt securities available for sale:
Agency residential mortgage-backed securities ("MBS")	$	258,150	$	6	$	(18,702	)	$	239,454
Securities of U.S. Government sponsored entities		308,768		2		(13,851	)		294,919
Obligations of states and political subdivisions		72,679		42		(1,438	)		71,283
Corporate securities		2,129,103		480		(220,035	)		1,909,548
Collateralized loan obligations		1,501,248		830		(17,481	)		1,484,597
Total debt securities available for sale		4,269,948		1,360		(271,507	)		3,999,801
Debt securities held to maturity:
Agency residential MBS		78,565		17		(5,270	)		73,312
Obligations of states and political subdivisions		71,182		47		(335	)		70,894
Corporate securities		728,650		84		(23,378	)		705,356
Total debt securities held to maturity		878,397		148		(28,983	)		849,562
Total	$	5,148,345	$	1,508	$	(300,490	)	$	4,849,363

	At December 31, 2022
			Gross		Gross
	Amortized		Unrealized		Unrealized			Fair
	Cost		Gains		Losses			Value
	(In thousands)
Debt securities available for sale:
Agency residential MBS	$	311,089	$	4	$	(25,045	)	$	286,048
Securities of U.S. Government sponsored entities		306,336		3		(15,486	)		290,853
Obligations of states and political subdivisions		84,024		59		(2,079	)		82,004
Corporate securities		2,406,566		1,032		(307,643	)		2,099,955
Collateralized loan obligations		1,587,326		527		(14,970	)		1,572,883
Total debt securities available for sale		4,695,341		1,625		(365,223	)		4,331,743
Debt securities held to maturity:
Agency residential MBS		104,852		13		(7,503	)		97,362
Obligations of states and political subdivisions		89,208		73		(538	)		88,743
Corporate securities		721,854		-		(34,448	)		687,406
Total debt securities held to maturity		915,914		86		(42,489	)		873,511
Total	$	5,611,255	$	1,711	$	(407,712	)	$	5,205,254

Investments Classified by Contractual Maturity Date [Table Text Block]

	At December 31, 2023
	Debt Securities Available				Debt Securities Held
	for Sale				to Maturity
	Amortized		Fair		Amortized		Fair
	Cost		Value		Cost		Value
	(In thousands)
Maturity in years:
1 year or less	$	52,703	$	52,357	$	15,117	$	15,095
Over 1 to 5 years		756,658		721,179		312,847		307,557
Over 5 to 10 years		1,701,189		1,502,214		471,868		453,598
Subtotal		2,510,550		2,275,750		799,832		776,250
Collateralized loan obligations		1,501,248		1,484,597		-		-
Agency residential MBS		258,150		239,454		78,565		73,312
Total	$	4,269,948	$	3,999,801	$	878,397	$	849,562

	At December 31, 2022
	Debt Securities Available				Debt Securities Held
	for Sale				to Maturity
	Amortized		Fair		Amortized		Fair
	Cost		Value		Cost		Value
	(In thousands)
Maturity in years:
1 year or less	$	251,578	$	250,317	$	12,676	$	12,659
Over 1 to 5 years		578,886		548,787		161,653		158,409
Over 5 to 10 years		1,966,462		1,673,708		636,733		605,081
Subtotal		2,796,926		2,472,812		811,062		776,149
Collateralized loan obligations		1,587,326		1,572,883		-		-
Agency residential MBS		311,089		286,048		104,852		97,362
Total	$	4,695,341	$	4,331,743	$	915,914	$	873,511

Schedule of Unrealized Loss on Investments 1 [Table Text Block]

	Debt Securities Available for Sale
	At December 31, 2023
	No. of		Less than 12 months					No. of		12 months or longer					No. of		Total
	Investment				Unrealized			Investment				Unrealized			Investment				Unrealized
	Positions		Fair Value		Losses			Positions		Fair Value		Losses			Positions		Fair Value		Losses
	($ in thousands)
Agency residential MBS		1	$	115	$	(2	)		107	$	238,642	$	(18,700	)		108	$	238,757	$	(18,702	)
Securities of U.S. Government sponsored entities		2		9,746		(15	)		19		278,265		(13,836	)		21		288,011		(13,851	)
Obligations of states and political subdivisions		2		2,280		(15	)		50		57,614		(1,423	)		52		59,894		(1,438	)
Corporate securities		-		-		-			151		1,894,602		(220,035	)		151		1,894,602		(220,035	)
Collateralized loan obligations		34		428,363		(8,914	)		67		578,643		(8,567	)		101		1,007,006		(17,481	)
Total		39	$	440,504	$	(8,946	)		394	$	3,047,766	$	(262,561	)		433	$	3,488,270	$	(271,507	)

	Debt Securities Held to Maturity
	At December 31, 2023
	No. of		Less than 12 months					No. of		12 months or longer					No. of		Total
	Investment				Unrecognized			Investment				Unrecognized			Investment				Unrecognized
	Positions		Fair Value		Losses			Positions		Fair Value		Losses			Positions		Fair Value		Losses
	($ in thousands)
Agency residential MBS		1	$	-	$	-			93	$	72,376	$	(5,270	)		94	$	72,376	$	(5,270	)
Obligations of states and political subdivisions		23		18,599		(90	)		26		25,466		(245	)		49		44,065		(335	)
Corporate securities		3		26,567		(1,184	)		46		641,598		(22,194	)		49		668,165		(23,378	)
Total		27	$	45,166	$	(1,274	)		165	$	739,440	$	(27,709	)		192	$	784,606	$	(28,983	)

	Debt Securities Available for Sale
	At December 31, 2022
	No. of		Less than 12 months					No. of		12 months or longer					No. of		Total
	Investment				Unrealized			Investment				Unrealized			Investment				Unrealized
	Positions		Fair Value		Losses			Positions		Fair Value		Losses			Positions		Fair Value		Losses
	($ in thousands)
Agency residential MBS		107	$	279,139	$	(24,222	)		9	$	6,110	$	(823	)		116	$	285,249	$	(25,045	)
Securities of U.S. Government sponsored entities		22		289,067		(15,486	)		-		-		-			22		289,067		(15,486	)
Obligations of states and political subdivisions		56		65,633		(1,902	)		8		3,265		(177	)		64		68,898		(2,079	)
Corporate securities		133		1,521,294		(170,453	)		56		555,727		(137,190	)		189		2,077,021		(307,643	)
Collateralized loan obligations		58		518,074		(13,772	)		20		192,692		(1,198	)		78		710,766		(14,970	)
Total		376	$	2,673,207	$	(225,835	)		93	$	757,794	$	(139,388	)		469	$	3,431,001	$	(365,223	)

	Debt Securities Held to Maturity
	At December 31, 2022
	No. of		Less than 12 months					No. of		12 months or longer					No. of		Total
	Investment				Unrecognized			Investment				Unrecognized			Investment				Unrecognized
	Positions		Fair Value		Losses			Positions		Fair Value		Losses			Positions		Fair Value		Losses
	($ in thousands)
Agency residential MBS		97	$	95,814	$	(7,404	)		2	$	682	$	(99	)		99	$	96,496	$	(7,503	)
Obligations of states and political subdivisions		54		53,536		(538	)		-		-		-			54		53,536		(538	)
Corporate securities		49		672,406		(34,448	)		-		-		-			49		672,406		(34,448	)
Total		200	$	821,756	$	(42,390	)		2	$	682	$	(99	)		202	$	822,438	$	(42,489	)

Debt Securities, Held-to-Maturity, Allowance for Credit Loss [Table Text Block]

	For the Years Ended December 31,
	2023		2022			2021
	(In thousands)
Allowance for credit losses:
Beginning balance	$	1	$	7		$	9
Reversal of provision for credit losses		-		(6	)		(2	)
Chargeoffs		-		-			-
Recoveries		-		-			-
Total ending balance	$	1	$	1		$	7

Debt Securities, Held-to-Maturity, Credit Quality Indicator [Table Text Block]

	Credit Risk Profile by Credit Rating
	At December 31, 2023
	AAA/AA/A		BBB+		Not Rated		Total
	(In thousands)
Agency residential MBS	$	78,092	$	-	$	473	$	78,565
Obligations of states and political subdivisions		71,002		-		180		71,182
Corporate securities		506,508		222,142		-		728,650
Total	$	655,602	$	222,142	$	653	$	878,397

Interest Income from Investments [Table Text Block]

	For the Years Ended December 31,
	2023		2022		2021
	(In thousands)
Taxable	$	221,742	$	158,465	$	106,329
Tax-exempt from regular federal income tax		4,484		5,819		8,424
Total interest income from investment securities	$	226,226	$	164,284	$	114,753