Securities (Tables)

6 Months Ended

Jun. 30, 2024

Securities Available for Sale

This table provides detailed information about securities available for sale at June 30, 2024 and December 31, 2023 (in thousands):

June 30, 2024	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
U.S. Treasury	$	809,122	$	773	$	(6,825	)	$	803,070
U.S. Agencies		661,737		—		(2,651	)		659,086
Mortgage-backed		4,315,860		812		(545,477	)		3,771,195
State and political subdivisions		1,315,005		110		(100,388	)		1,214,727
Corporates		346,030		—		(25,675	)		320,355
Collateralized loan obligations		338,285		942		(287	)		338,940
Total	$	7,786,039	$	2,637	$	(681,303	)	$	7,107,373

December 31, 2023	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
U.S. Treasury	$	1,308,689	$	254	$	(10,201	)	$	1,298,742
U.S. Agencies		162,406		252		(2,937	)		159,721
Mortgage-backed		4,128,576		949		(508,740	)		3,620,785
State and political subdivisions		1,359,744		2,218		(74,987	)		1,286,975
Corporates		382,069		—		(30,794	)		351,275
Collateralized loan obligations		351,376		811		(1,072	)		351,115
Total	$	7,692,860	$	4,484	$	(628,731	)	$	7,068,613

Gross Unrealized Losses and Fair Value of Investment Securities Available for Sale

The following table shows the Company’s available-for-sale investments’ gross unrealized losses and fair value, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position, at June 30, 2024 and December 31, 2023 (in thousands):

	Less than 12 months							12 months or more							Total
June 30, 2024	Count		Fair Value		Unrealized Losses			Count		Fair Value		Unrealized Losses			Count		Fair Value		Unrealized Losses
Description of Securities
U.S. Treasury		60	$	414,665	$	(2,430	)		13	$	172,775	$	(4,395	)		73	$	587,440	$	(6,825	)
U.S. Agencies		13		571,388		(728	)		7		87,698		(1,923	)		20		659,086		(2,651	)
Mortgage-backed		54		360,634		(3,343	)		848		3,262,160		(542,134	)		902		3,622,794		(545,477	)
State and political subdivisions		306		214,127		(11,309	)		1,677		958,321		(89,079	)		1,983		1,172,448		(100,388	)
Corporates		—		—		—			249		320,355		(25,675	)		249		320,355		(25,675	)
Collateralized loan obligations		12		89,819		(135	)		9		66,473		(152	)		21		156,292		(287	)
Total		445	$	1,650,633	$	(17,945	)		2,803	$	4,867,782	$	(663,358	)		3,248	$	6,518,415	$	(681,303	)

	Less than 12 months							12 months or more							Total
December 31, 2023	Count		Fair Value		Unrealized Losses			Count		Fair Value		Unrealized Losses			Count		Fair Value		Unrealized Losses
Description of Securities
U.S. Treasury		8	$	509,946	$	(267	)		63	$	745,573	$	(9,934	)		71	$	1,255,519	$	(10,201	)
U.S. Agencies		—		—		—			16		116,324		(2,937	)		16		116,324		(2,937	)
Mortgage-backed		14		19,154		(476	)		852		3,526,296		(508,264	)		866		3,545,450		(508,740	)
State and political subdivisions		388		200,835		(9,202	)		1,476		890,545		(65,785	)		1,864		1,091,380		(74,987	)
Corporates		—		—		—			267		351,275		(30,794	)		267		351,275		(30,794	)
Collateralized loan obligations		1		4,246		(4	)		32		210,872		(1,068	)		33		215,118		(1,072	)
Total		411	$	734,181	$	(9,949	)		2,706	$	5,840,885	$	(618,782	)		3,117	$	6,575,066	$	(628,731	)

Gross Unrealized Losses and Fair Value of Investment Securities Held to Maturity

The following table shows the Company’s held-to-maturity investments’ gross unrealized losses and fair value, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position, at June 30, 2024 and December 31, 2023, respectively (in thousands):

	Less than 12 months							12 months or more							Total
June 30, 2024	Count		Fair Value		Unrealized Losses			Count		Fair Value		Unrealized Losses			Count		Fair Value		Unrealized Losses
U.S. Agencies		—	$	—	$	—			10	$	113,997	$	(2,273	)		10	$	113,997	$	(2,273	)
Mortgage-backed		4		2,141		(47	)		265		2,208,664		(421,809	)		269		2,210,805		(421,856	)
State and political subdivisions		56		273,506		(13,253	)		1,432		1,850,868		(212,739	)		1,488		2,124,374		(225,992	)
Total		60	$	275,647	$	(13,300	)		1,707	$	4,173,529	$	(636,821	)		1,767	$	4,449,176	$	(650,121	)

	Less than 12 months							12 months or more							Total
December 31, 2023	Count		Fair Value		Unrealized Losses			Count		Fair Value		Unrealized Losses			Count		Fair Value		Unrealized Losses
U.S. Agency		—	$	—	$	—			11	$	120,524	$	(2,686	)		11	$	120,524	$	(2,686	)
Mortgage-backed		2		1,469		(14	)		263		2,377,922		(356,643	)		265		2,379,391		(356,657	)
State and political subdivisions		146		570,950		(22,557	)		1,343		1,612,442		(147,640	)		1,489		2,183,392		(170,197	)
Total		148	$	572,419	$	(22,571	)		1,617	$	4,110,888	$	(506,969	)		1,765	$	4,683,307	$	(529,540	)

Schedule of Amortized Cost Basis by Credit Rating of Held to Maturity Investment

The following tables show the amortized cost basis by credit rating of the Company’s held-to-maturity investments at June 30, 2024 and December 31, 2023 (in thousands):

	Amortized Cost Basis by Credit Rating - HTM Debt Securities
June 30, 2024	AAA		AA		A		BBB		BB		CCC-C		Total
State and political subdivisions:
Competitive	$	—	$	9,080	$	442,509	$	641,441	$	30,112	$	22,134	$	1,145,276
Utilities		1,577,195		—		52,788		25,400		—		—		1,655,383
Total state and political subdivisions	$	1,577,195	$	9,080	$	495,297	$	666,841	$	30,112	$	22,134	$	2,800,659

	Amortized Cost Basis by Credit Rating - HTM Debt Securities
December 31, 2023	AAA		AA		A		BBB		BB		B		CCC-C		Total
State and political subdivisions:
Competitive	$	—	$	7,704	$	464,349	$	641,743	$	30,734	$	15,326	$	2,649	$	1,162,505
Utilities		757,381		795,448		87,736		26,720		615		—		—		1,667,900
Total state and political subdivisions	$	757,381	$	803,152	$	552,085	$	668,463	$	31,349	$	15,326	$	2,649	$	2,830,405

Schedule of Aging of Past Due Held to Maturity Securities

The following table presents the aging of past due held-to-maturity securities at June 30, 2024 (in thousands):

June 30, 2024	30-89 Days Past Due and Accruing		Greater than 90 Days Past Due and Accruing		Non- Accrual		Total Past Due		Current		Total
State and political subdivisions:
Competitive	$	40,570	$	—	$	—	$	40,570	$	1,104,706	$	1,145,276
Utilities		—		—		—		—		1,655,383		1,655,383
Total state and political subdivisions	$	40,570	$	—	$	—	$	40,570	$	2,760,089	$	2,800,659

Schedule of Other Securities

The table below provides detailed information for Other securities at June 30, 2024 and December 31, 2023 (in thousands):

	June 30, 2024		December 31, 2023
FRB and FHLB stock	$	65,172	$	87,672
Equity securities with readily determinable fair values		11,355		11,228
Equity securities without readily determinable fair values		371,123		394,035
Total	$	447,650	$	492,935

Schedule of Components of Investment Securities (Losses) Gains, Net

The table below presents the components of Investments securities (losses) gains, net for the three and six months ended June 30, 2024 and June 30, 2023 (in thousands):

	Three Months Ended June 30,						Six Months Ended June 30,
	2024			2023			2024			2023
Investment securities (losses) gains, net
Available-for-sale debt securities:
Gains realized on sales	$	—		$	—		$	139		$	—
Losses realized on sales		—			—			—			(2	)
Impairment of AFS security		—			(125	)		—			(4,925	)
Equity securities with readily determinable fair values:
Fair value adjustments, net		(26	)		(62	)		(49	)		26
Equity securities without readily determinable fair values:
Fair value adjustments, net		(2,565	)		1,087			(3,015	)		477
Sales		724			—			10,429			—
Total investment securities (losses) gains, net	$	(1,867	)	$	900		$	7,504		$	(4,424	)

Available-for-sale Securities [Member]

Contractual Maturity Information

The following table presents contractual maturity information for securities available for sale at June 30, 2024 (in thousands):

	Amortized		Fair
	Cost		Value
Due in 1 year or less	$	898,944	$	892,089
Due after 1 year through 5 years		1,452,834		1,422,180
Due after 5 years through 10 years		612,812		574,807
Due after 10 years		505,589		447,102
Total		3,470,179		3,336,178
Mortgage-backed securities		4,315,860		3,771,195
Total securities available for sale	$	7,786,039	$	7,107,373

Held-to-maturity Securities [Member]

Contractual Maturity Information

The following table provides detailed information about securities held to maturity at June 30, 2024 and December 31, 2023, respectively (in thousands):

June 30, 2024	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value		Allowance for Credit Losses			Net Carrying Amount
U.S. Agencies	$	116,270	$	—	$	(2,273	)	$	113,997	$	—		$	116,270
Mortgage-backed		2,632,661		—		(421,856	)		2,210,805		—			2,632,661
State and political subdivisions		2,800,659		13,939		(225,992	)		2,588,606		(2,956	)		2,797,703
Total	$	5,549,590	$	13,939	$	(650,121	)	$	4,913,408	$	(2,956	)	$	5,546,634

December 31, 2023	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value		Allowance for Credit Losses			Net Carrying Amount
U.S. Agencies	$	123,210	$	—	$	(2,686	)	$	120,524	$	—		$	123,210
Mortgage-backed		2,738,253		18		(356,657	)		2,381,614		—			2,738,253
State and political subdivisions		2,830,405		21,021		(170,197	)		2,681,229		(3,258	)		2,827,147
Total	$	5,691,868	$	21,039	$	(529,540	)	$	5,183,367	$	(3,258	)	$	5,688,610

The following table presents contractual maturity information for securities held to maturity at June 30, 2024 (in thousands):

	Amortized		Fair
	Cost		Value
Due in 1 year or less	$	232,274	$	229,504
Due after 1 year through 5 years		222,096		216,413
Due after 5 years through 10 years		802,704		754,813
Due after 10 years		1,659,855		1,501,873
Total		2,916,929		2,702,603
Mortgage-backed securities		2,632,661		2,210,805
Total securities held to maturity	$	5,549,590	$	4,913,408