This table provides detailed information about securities available for sale at March 31, 2022 and December 31, 2021 (in thousands):

March 31, 2022	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
U.S. Treasury	$	388,866	$	58	$	(6,789	)	$	382,135
U.S. Agencies		153,489		554		(1,265	)		152,778
Mortgage-backed		5,679,853		15,184		(286,815	)		5,408,222
State and political subdivisions		2,101,114		18,327		(72,930	)		2,046,511
Corporates		381,163		252		(15,330	)		366,085
Collateralized loan obligations		194,364		12		(14	)		194,362
Total	$	8,898,849	$	34,387	$	(383,143	)	$	8,550,093

December 31, 2021	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
U.S. Treasury	$	69,551	$	374	$	(751	)	$	69,174
U.S. Agencies		121,681		3,252		(1	)		124,932
Mortgage-backed		7,967,537		93,390		(95,872	)		7,965,055
State and political subdivisions		3,270,160		161,674		(9,146	)		3,422,688
Corporates		316,840		2,504		(1,498	)		317,846
Collateralized loan obligations		76,815		4		—			76,819
Total	$	11,822,584	$	261,198	$	(107,268	)	$	11,976,514

The following table presents contractual maturity information for securities available for sale at March 31, 2022 (in thousands):

	Amortized		Fair
	Cost		Value
Due in 1 year or less	$	123,219	$	123,499
Due after 1 year through 5 years		1,141,112		1,121,962
Due after 5 years through 10 years		699,721		686,107
Due after 10 years		1,254,944		1,210,303
Total		3,218,996		3,141,871
Mortgage-backed securities		5,679,853		5,408,222
Total securities available for sale	$	8,898,849	$	8,550,093

Securities may be disposed of before contractual maturities due to sales by the Company or because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties.

For the three months ended March 31, 2022, there were no sales of securities available for sale. For the three months ended March 31, 2021 there were $129.1 million in proceeds from sales of securities available for sale.

There were no gross realized gains for the three months ended March 31, 2022. Securities transactions resulted in gross realized gains of $2.7 million for the three months ended March 31, 2021. There were no gross realized losses for either the three months ended March 31, 2022 or 2021.

There were $9.3 billion and $10.2 billion of securities pledged to secure U.S. Government deposits, other public deposits, certain trust deposits, derivative transactions, and repurchase agreements at March 31, 2022 and December 31, 2021, respectively. Of these amounts, $148.7 million and $171.2 million of securities at March 31, 2022 and December 31, 2021, respectively, were pledged at the Federal Reserve Discount Window but were unencumbered as of those dates.

Accrued interest on securities available for sale totaled $27.1 million and $45.8 million as of March 31, 2022 and December 31, 2021, respectively, and is included in the Accrued income line on the Company’s Consolidated Balance Sheets. The total amount of accrued interest is excluded from the amortized cost of available-for-sale securities presented above. Further, the Company has elected not to measure an ACL for accrued interest receivable.

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 March 31, 2022 and December 31, 2021 (in thousands):

	Less than 12 months							12 months or more							Total
March 31, 2022	Count		Fair Value		Unrealized Losses			Count		Fair Value		Unrealized Losses			Count		Fair Value		Unrealized Losses
Description of Securities
U.S. Treasury		35	$	364,450	$	(6,789	)		—	$	—	$	—			35	$	364,450	$	(6,789	)
U.S. Agencies		5		63,274		(1,265	)		—		—		—			5		63,274		(1,265	)
Mortgage-backed		659		4,316,175		(269,158	)		12		207,738		(17,657	)		671		4,523,913		(286,815	)
State and political subdivisions		1,302		1,043,982		(62,299	)		60		65,444		(10,631	)		1,362		1,109,426		(72,930	)
Corporates		241		327,050		(15,230	)		2		4,044		(100	)		243		331,094		(15,330	)
Collateralized loan obligations		6		31,220		(14	)		—		—		—			6		31,220		(14	)
Total		2,248	$	6,146,151	$	(354,755	)		74	$	277,226	$	(28,388	)		2,322	$	6,423,377	$	(383,143	)

	Less than 12 months							12 months or more							Total
December 31, 2021	Count		Fair Value		Unrealized Losses			Count		Fair Value		Unrealized Losses			Count		Fair Value		Unrealized Losses
Description of Securities
U.S. Treasury		4	$	58,867	$	(751	)		—	$	—	$	—			4	$	58,867	$	(751	)
U.S. Agencies		1		11,149		(1	)		—		—		—			1		11,149		(1	)
Mortgage-backed		344		5,404,968		(87,301	)		13		233,295		(8,571	)		357		5,638,263		(95,872	)
State and political subdivisions		357		329,042		(6,969	)		31		44,939		(2,177	)		388		373,981		(9,146	)
Corporates		152		193,899		(1,498	)		—		—		—			152		193,899		(1,498	)
Collateralized loan obligations		—		—		—			—		—		—			—		—		—
Total		858	$	5,997,925	$	(96,520	)		44	$	278,234	$	(10,748	)		902	$	6,276,159	$	(107,268	)

The unrealized losses in the Company’s investments were caused by changes in interest rates, and not from a decline in credit of the underlying issuers. The U.S. Treasury, U.S. Agency, and GSE mortgage-backed securities are all considered to be agency-backed securities with no risk of loss as they are either explicitly or implicitly guaranteed by the U.S. government. The changes in fair value in the agency-backed portfolios are solely driven by change in interest rates caused by changing economic conditions. The Company has no knowledge of any

underlying credit issues and the cash flows underlying the debt securities have not changed and are not expected to be impacted by changes in interest rates.

For the State and political subdivision portfolio, the majority of the Company’s holdings are in general obligation bonds, which have a very low historical default rate due to issuers generally having unlimited taxing authority to service the debt. For the State and political, Corporate, and Collateralized loan obligations portfolios, the Company has a robust process for monitoring credit risk, including both pre-purchase and ongoing post-purchase credit reviews and analysis. The Company monitors credit ratings of all bond issuers in these segments and reviews available financial data, including market and sector trends.

As of March 31, 2022 and December 31, 2021, there was no ACL related to the Company’s available-for-sale securities as the decline in fair value did not result from credit issues.

The following table shows the Company’s held-to-maturity investments’ amortized cost, fair value, and gross unrealized gains and losses at March 31, 2022 and December 31, 2021, respectively (in thousands):

March 31, 2022	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value		Allowance for Credit Losses			Net Carrying Amount
U.S. Agencies	$	6,000	$	4	$	—		$	6,004	$	—		$	6,000
Mortgage-backed		2,490,693		10		(66,501	)		2,424,202		—			2,490,693
State and political subdivisions		2,105,539		363		(142,653	)		1,963,249		(2,045	)		2,103,494
Total	$	4,602,232	$	377	$	(209,154	)	$	4,393,455	$	(2,045	)	$	4,600,187

December 31, 2021	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value		Allowance for Credit Losses			Net Carrying Amount
Mortgage-backed	$	396,134	$	14	$	(2,431	)	$	393,717	$	—		$	396,134
State and political subdivisions		1,084,282		3,346		(38,954	)		1,048,674		(1,940	)		1,082,342
Total	$	1,480,416	$	3,360	$	(41,385	)	$	1,442,391	$	(1,940	)	$	1,478,476

The following table presents contractual maturity information for securities held to maturity at March 31, 2022 (in thousands):

	Amortized		Fair
	Cost		Value
Due in 1 year or less	$	13,819	$	13,784
Due after 1 year through 5 years		151,022		144,816
Due after 5 years through 10 years		616,835		579,542
Due after 10 years		1,329,863		1,231,111
Total		2,111,539		1,969,253
Mortgage-backed securities		2,490,693		2,424,202
Total securities held to maturity	$	4,602,232	$	4,393,455

Expected maturities will differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties.

There were no sales of securities held to maturity during the three months ended March 30, 2022 or 2021.

During the first quarter of 2022, securities with an amortized cost of $3.0 billion and a fair value of $2.9 billion were transferred from the available-for-sale classification to the held-to-maturity classification as the Company has the positive intent and ability to hold these securities to maturity. The transfer of securities was made at fair value at the time of transfer. The unrealized holding loss at the time of transfer is retained in AOCI and will be amortized over the remaining life of the securities, offsetting the related amortization of discount or premium on the transferred securities. No gains or losses were recognized at the time of the transfer. The amortized cost balance of securities held to maturity in the tables above includes a net unamortized unrealized loss of $155.7 million at March 31, 2022.

Accrued interest on securities held to maturity totaled $17.0 million and $5.3 million as March 31, 2022 and December 31, 2021, respectively, and is included in the Accrued income line on the Company’s Consolidated Balance Sheets. The total amount of accrued interest is excluded from the amortized cost of held-to-maturity securities presented above. Further, the Company has elected not to measure an ACL for accrued interest receivable.

The following table shows the Company’s held-to-maturity investments’ gross unrealized losses and fair value, aggregated by length of time that individual securities have been in a continuous unrealized loss position, at March 31, 2022 and December 31, 2021, respectively (in thousands):

	Less than 12 months							12 months or more							Total
March 31, 2022	Count		Fair Value		Unrealized Losses			Count		Fair Value		Unrealized Losses			Count		Fair Value		Unrealized Losses
U.S. Agencies		—	$	—	$	—			—	$	—	$	—			—	$	—	$	—
Mortgage-backed		194		2,404,509		(66,501	)		—		—		—			194		2,404,509		(66,501	)
State and political subdivisions		1,205		1,625,062		(96,594	)		41		332,118		(46,059	)		1,246		1,957,180		(142,653	)
Total		1,399	$	4,029,571	$	(163,095	)		41	$	332,118	$	(46,059	)		1,440	$	4,361,689	$	(209,154	)

	Less than 12 months							12 months or more							Total
December 31, 2021	Count		Fair Value		Unrealized Losses			Count		Fair Value		Unrealized Losses			Count		Fair Value		Unrealized Losses
Mortgage-backed		12	$	317,887	$	(2,431	)		—	$	—	$	—			12	$	317,887	$	(2,431	)
State and political subdivisions		58		585,153		(12,494	)		28		217,579		(26,460	)		86		802,732		(38,954	)
Total		70	$	903,040	$	(14,925	)		28	$	217,579	$	(26,460	)		98	$	1,120,619	$	(41,385	)

The unrealized losses in the Company’s held-to-maturity portfolio were caused by changes in the interest rate environment. The U.S. Agency and GSE mortgage-backed securities are considered to be agency-backed securities with no risk of loss as they are either explicitly or implicitly guaranteed by the U.S. government. Therefore, the Company’s expected lifetime loss for these portfolios is zero and there is no ACL recorded for this portfolio. The Company has no knowledge of any underlying credit issues and the cash flows underlying the debt securities have not changed and are not expected to be impacted by changes in interest rates.

For the State and political subdivision portfolio, the Company’s holdings are in general obligation bonds as well as private placement bonds, which have very low historical default rates due to issuers generally having unlimited taxing authority to service the debt. The Company has a robust process for monitoring credit risk, including both pre-purchase and ongoing post-purchase credit reviews and analysis. The Company monitors credit ratings of all bond issuers in these segments and reviews available financial data, including market and sector trends. The underlying bonds are evaluated for credit losses in conjunction with management’s estimate of the ACL based on credit rating.

The following tables show the amortized cost basis by credit rating of the Company’s held-to-maturity investments at March 31, 2022 and December 31, 2021 (in thousands):

	Amortized Cost Basis by Credit Rating - HTM Debt Securities
March 31, 2022	AAA		AA		A		BBB		BB		CCC-C		Total
State and political subdivisions:
Competitive	$	—	$	—	$	379,924	$	560,001	$	20,219	$	830	$	960,974
Utilities		342,489		690,649		81,855		29,572		—		—		1,144,565
Total state and political subdivisions	$	342,489	$	690,649	$	461,779	$	589,573	$	20,219	$	830	$	2,105,539

	Amortized Cost Basis by Credit Rating - HTM Debt Securities
December 31, 2021	A		BBB		BB		CCC-C		Total
State and political subdivisions:
Competitive	$	372,696	$	605,104	$	20,678	$	870	$	999,348
Utilities		55,096		29,838		—		—		84,934
Total state and political subdivisions	$	427,792	$	634,942	$	20,678	$	870	$	1,084,282

Competitive held-to-maturity securities include not-for-profit enterprises that provide public functions such as housing, higher education or healthcare, but do so in a competitive environment. It also includes project financings that can have relatively high enterprise risk, such as deals backed by revenues from sports or convention facilities or start-up transportation ventures.

Utilities are public enterprises providing essential services with a monopoly or near-monopoly over the service area. This includes environmental utilities (water, sewer, solid waste), power utilities (electric distribution and generation, gas), and transportation utilities (airports, parking, toll roads, mass transit, ports).

All held-to-maturity securities were current and not past due at March 31, 2022.

The following table presents the aging of past due held-to-maturity securities at December 31, 2021 (in thousands):

December 31, 2021	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	$	7,795	$	—	$	—	$	7,795	$	991,553	$	999,348
Utilities		—		—		—		—		84,934		84,934
Total state and political subdivisions	$	7,795	$	—	$	—	$	7,795	$	1,076,487	$	1,084,282

There were net unrealized losses on trading securities of $280 thousand and net unrealized losses of $40 thousand at March 31, 2022 and 2021, respectively. Net unrealized gains and losses are included in trading and investment banking income on the Company’s Consolidated Statements of Income. Securities sold not yet purchased

totaled $1.6 million and $3.2 million at March 31, 2022 and December 31, 2021, respectively, and are classified within the Other liabilities line of the Company’s Consolidated Balance Sheets.

The table below provides detailed information for Other securities at March 31, 2022 and December 31, 2021 (in thousands):

Investment in FRB stock is based on the capital structure of the investing bank, and investment in FHLB stock is mainly tied to the level of borrowings from the FHLB. These holdings are carried at cost. Equity securities with readily determinable fair values are generally traded on an exchange and market prices are readily available. Equity securities without readily determinable fair values include equity investments which are held by a subsidiary qualified as a Small Business Investment Company, as well as investments in low-income housing partnerships within the areas the Company serves. Unrealized gains or losses on equity securities with and without readily determine fair values are recognized in the Investment securities losses, net line of the Company’s Consolidated Statements of Income.

The table below presents the components of Investments securities losses, net for the three months ended March 31, 2022 and March 31, 2021 (in thousands):

	Three Months Ended March 31,
	2022			2021
Investment securities losses, net
Available-for-sale debt securities:
Gains realized on sales	$	—		$	2,720
Equity securities with readily determinable fair values:
Fair value adjustments, net		(1,722	)		(13,918	)
Equity securities without readily determinable fair values:
Fair value adjustments, net		1,200			2,862
Total investment securities losses, net	$	(522	)	$	(8,336	)