Note 2 - Investment Securities (Tables)

12 Months Ended

Dec. 31, 2021

Notes Tables

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

	At December 31, 2021
			Gross		Gross
	Amortized		Unrealized		Unrealized			Fair
	Cost		Gains		Losses			Value
	(In thousands)
Debt securities available for sale
Agency residential mortgage-backed securities ("MBS")	$	399,997	$	11,766	$	(37	)	$	411,726
Securities of U.S. Government entities		119		-		-			119
Obligations of states and political subdivisions		90,107		3,842		(29	)		93,920
Corporate securities		2,692,792		63,573		(9,630	)		2,746,735
Collateralized loan obligations		1,385,331		1,743		(719	)		1,386,355
Total debt securities available for sale		4,568,346		80,924		(10,415	)		4,638,855
Debt securities held to maturity
Agency residential MBS		147,632		3,112		(18	)		150,726
Non-agency residential MBS		758		2		(19	)		741
Obligations of states and political subdivisions		158,013		3,082		-			161,095
Total debt securities held to maturity		306,403		6,196		(37	)		312,562
Total	$	4,874,749	$	87,120	$	(10,452	)	$	4,951,417

	At December 31, 2020
			Gross		Gross
	Amortized		Unrealized		Unrealized			Fair
	Cost		Gains		Losses			Value
	(In thousands)
Debt securities available for sale
Agency residential MBS	$	630,174	$	22,779	$	(1	)	$	652,952
Securities of U.S. Government entities		154		-		-			154
Obligations of states and political subdivisions		105,679		5,332		(1	)		111,010
Corporate securities		1,986,995		131,025		(42	)		2,117,978
Commercial paper		24,983		7		-			24,990
Collateralized loan obligations		1,152,766		4,433		(1,098	)		1,156,101
Total debt securities available for sale		3,900,751		163,576		(1,142	)		4,063,185
Debt securities held to maturity
Agency residential MBS		240,332		6,852		(32	)		247,152
Non-agency residential MBS		1,344		26		-			1,370
Obligations of states and political subdivisions		273,922		7,243		-			281,165
Total debt securities held to maturity		515,598		14,121		(32	)		529,687
Total	$	4,416,349	$	177,697	$	(1,174	)	$	4,592,872

Investments Classified by Contractual Maturity Date [Table Text Block]

	At December 31, 2021
	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	$	306,333	$	309,257	$	15,836	$	15,941
Over 1 to 5 years		707,062		738,057		125,001		127,539
Over 5 to 10 years		2,320,559		2,347,242		17,176		17,615
Over 10 years		834,395		832,573		-		-
Subtotal		4,168,349		4,227,129		158,013		161,095
MBS		399,997		411,726		148,390		151,467
Total	$	4,568,346	$	4,638,855	$	306,403	$	312,562

	At December 31, 2020
	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	$	212,140	$	213,715	$	54,526	$	54,927
Over 1 to 5 years		922,170		974,438		129,786		133,195
Over 5 to 10 years		1,767,747		1,851,184		89,610		93,043
Over 10 years		368,520		370,896		-		-
Subtotal		3,270,577		3,410,233		273,922		281,165
MBS		630,174		652,952		241,676		248,522
Total	$	3,900,751	$	4,063,185	$	515,598	$	529,687

Schedule of Unrealized Loss on Investments [Table Text Block]

	Debt Securities Available for Sale
	At December 31, 2021
	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		7	$	8,900	$	(37	)		2	$	47	$	-			9	$	8,947	$	(37	)
Securities of U.S. Government entities		-		-		-			1		119		-			1		119		-
Obligations of states and political subdivisions		6		2,859		(27	)		2		669		(2	)		8		3,528		(29	)
Corporate securities		56		691,555		(9,630	)		-		-		-			56		691,555		(9,630	)
Collateralized loan obligations		19		208,199		(521	)		8		51,523		(198	)		27		259,722		(719	)
Total		88	$	911,513	$	(10,215	)		13	$	52,358	$	(200	)		101	$	963,871	$	(10,415	)

	Debt Securities Held to Maturity
	At December 31, 2021
	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		-	$	-	$	-			3	$	530	$	(18	)		3	$	530	$	(18	)
Non-agency residential MBS		1		542		(19	)		-		-		-			1		542		(19	)
Total		1	$	542	$	(19	)		3	$	530	$	(18	)		4	$	1,072	$	(37	)

	Debt Securities Available for Sale
	At December 31, 2020
	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	$	96	$	(1	)		1	$	17	$	-			2	$	113	$	(1	)
Securities of U.S. Government entities		1		154		-			-		-		-			1		154		-
Obligations of states and political subdivisions		2		692		(1	)		-		-		-			2		692		(1	)
Corporate securities		-		-		-			1		14,963		(42	)		1		14,963		(42	)
Collateralized loan obligations		36		268,584		(1,098	)		-		-		-			36		268,584		(1,098	)
Total		40	$	269,526	$	(1,100	)		2	$	14,980	$	(42	)		42	$	284,506	$	(1,142	)

	Debt Securities Held to Maturity
	At December 31, 2020
	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		3	$	377	$	(1	)		3	$	788	$	(31	)		6	$	1,165	$	(32	)

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

	For the Year Ended December 31,
	2021			2020
	(In thousands)
Allowance for credit losses:
Balance, end of prior period	$	9		$	-
Impact of adopting ASU 2016-13		-			16
Beginning balance		9			16
Reversal of provision		(2	)		(7	)
Chargeoffs		-			-
Recoveries		-			-
Total ending balance	$	7		$	9

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

	Credit Risk Profile by Credit Rating
	At December 31, 2021
	AAA/AA/A		B-		Not Rated		Total
	(In thousands)
Agency residential MBS	$	177	$	-	$	147,455	$	147,632
Non-agency residential MBS		149		561		48		758
Obligations of states and political subdivisions		155,268		-		2,745		158,013
Total	$	155,594	$	561	$	150,248	$	306,403

Interest Income from Investments [Table Text Block]

	For the Years Ended December 31,
	2021		2020		2019
	(In thousands)
Taxable	$	106,329	$	93,163	$	77,800
Tax-exempt from regular federal income tax		8,424		12,151		15,736
Total interest income from investment securities	$	114,753	$	105,314	$	93,536