Held-to-maturity securities (“HTM”), which include any security for which the Company has both the positive intent and ability to hold until maturity, are carried at historical cost adjusted for amortization of premiums and accretion of discounts. Premiums and discounts are amortized and accreted, respectively, to interest income using the constant effective yield method over the security’s estimated life. Prepayments are anticipated for mortgage-backed and SBA securities. Premiums on callable securities are amortized to their earliest call date.

Available-for-sale securities (“AFS”), which include any security for which the Company has no immediate plan to sell but which may be sold in the future, are carried at fair value. Realized gains and losses, based on specifically identified amortized cost of the individual security, are included in other income. Unrealized gains and losses are recorded, net of related income tax effects, in stockholders’ equity, further discussed below. Premiums and discounts are amortized and accreted, respectively, to interest income using the constant effective yield method over the estimated life of the security. Prepayments are anticipated for mortgage-backed and SBA securities. Premiums on callable securities are amortized to their earliest call date.

During the quarters ended June 30, 2022 and September 30, 2021, the Company transferred, at fair value, $1.99 billion and $500.8 million, respectively, of securities from the available-for-sale portfolio to the held-to-maturity portfolio. As of June 30, 2023, the related remaining combined net unrealized losses of $136.0 million in accumulated other comprehensive income (loss) will be amortized over the remaining life of the securities. No gains or losses on these securities were recognized at the time of transfer.


(In thousands)	Amortized Cost		Allowance for Credit Losses		Net Carrying Amount		Gross Unrealized Gains		Gross Unrealized (Losses)		Estimated Fair Value
Held-to-maturity

June 30, 2023
U.S. Government agencies	$	451,737	$	—	$	451,737	$	—	$	(94,515)	$	357,222
Mortgage-backed securities	1,193,118		—		1,193,118		—		(118,728)		1,074,390
State and political subdivisions	1,859,956		(934)		1,859,022		67		(415,230)		1,443,859
Other securities	255,157		(2,280)		252,877		—		(33,490)		219,387
Total HTM	$	3,759,968	$	(3,214)	$	3,756,754	$	67	$	(661,963)	$	3,094,858

December 31, 2022
U.S. Government agencies	$	448,012	$	—	$	448,012	$	—	$	(102,558)	$	345,454
Mortgage-backed securities	1,190,781		—		1,190,781		227		(118,960)		1,072,048
State and political subdivisions	1,861,102		(110)		1,860,992		56		(446,198)		1,414,850
Other securities	261,199		(1,278)		259,921		—		(29,040)		230,881
Total HTM	$	3,761,094	$	(1,388)	$	3,759,706	$	283	$	(696,756)	$	3,063,233

Mortgage-backed securities (“MBS”) are commercial MBS, secured by commercial properties, and residential MBS, generally secured by single-family residential properties. All mortgage-backed securities included in the table above were issued by U.S. government agencies or corporations. As of June 30, 2023, HTM MBS consists of $144.9 million and $1.05 billion of commercial MBS and residential MBS, respectively. As of December 31, 2022, HTM MBS consists of $149.2 million and $1.04 billion of commercial MBS and residential MBS, respectively.


(In thousands)	Amortized Cost		Allowance for Credit Losses		Gross Unrealized Gains		Gross Unrealized (Losses)		Estimated Fair Value
Available-for-sale

June 30, 2023
U.S. Treasury	$	2,271	$	—	$	—	$	(62)	$	2,209
U.S. Government agencies	183,735		—		51		(7,222)		176,564
Mortgage-backed securities	2,532,234		—		4		(249,910)		2,282,328
State and political subdivisions	1,029,164		—		184		(143,843)		885,505
Other securities	264,861		(2,396)		—		(29,313)		233,152
Total AFS	$	4,012,265	$	(2,396)	$	239	$	(430,350)	$	3,579,758

December 31, 2022
U.S. Treasury	$	2,257	$	—	$	—	$	(60)	$	2,197
U.S. Government agencies	191,498		—		103		(7,322)		184,279
Mortgage-backed securities	2,809,319		—		20		(266,437)		2,542,902
State and political subdivisions	1,056,124		—		250		(185,300)		871,074
Other securities	272,215		—		—		(19,813)		252,402
Total AFS	$	4,331,413	$	—	$	373	$	(478,932)	$	3,852,854

As of June 30, 2023, AFS MBS consists of $898.2 million and $1.38 billion of commercial MBS and residential MBS, respectively. As of December 31, 2022, AFS MBS consists of $1.07 billion and $1.47 billion of commercial MBS and residential MBS, respectively.

Accrued interest receivable on HTM and AFS securities at June 30, 2023 was $20.7 million and $16.6 million, respectively, and is included in interest receivable on the consolidated balance sheets. The Company has made the election to exclude all accrued interest receivable from securities from the estimate of credit losses.

The following table summarizes the Company’s AFS investments in an unrealized loss position for which an allowance for credit loss has not been recorded as of June 30, 2023, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position:


	Less Than 12 Months				12 Months or More				Total
(In thousands)	Estimated Fair Value		Gross Unrealized Losses		Estimated Fair Value		Gross Unrealized Losses		Estimated Fair Value		Gross Unrealized Losses
Available-for-sale
U.S. Treasury	$	776	$	(21)	$	1,433	$	(41)	$	2,209	$	(62)
U.S. Government agencies	22,246		(95)		149,445		(7,127)		171,691		(7,222)
Mortgage-backed securities	2,707		(85)		2,270,299		(249,825)		2,273,006		(249,910)
State and political subdivisions	17,045		(379)		846,298		(143,464)		863,343		(143,843)
Other securities	48,806		(7,261)		173,215		(19,656)		222,021		(26,917)
Total AFS	$	91,580	$	(7,841)	$	3,440,690	$	(420,113)	$	3,532,270	$	(427,954)

As of June 30, 2023, the Company’s investment portfolio included $3.58 billion of AFS securities, of which $3.53 billion, or 98.7%, were in an unrealized loss position that were not deemed to have credit losses. A portion of the unrealized losses were related to the Company’s MBS, which are issued and guaranteed by U.S. government-sponsored entities and agencies, and the Company’s state and political subdivision securities, specifically investments in insured fixed rate municipal bonds for which the issuers continue to make timely principal and interest payments under the contractual terms of the securities.

Furthermore, the decline in fair value for each of the above AFS securities is attributable to the rates for those investments yielding less than current market rates. Management does not believe any of the securities are impaired due to reasons of credit quality. Management believes the declines in fair value for the securities are temporary. Management does not have the intent to sell the securities, and management believes it is more likely than not the Company will not have to sell the securities before recovery of their amortized cost basis.

All MBS held by the Company are issued by U.S. government-sponsored entities and agencies. These securities are either explicitly or implicitly guaranteed by the U.S. government, highly rated by major rating agencies and have a long history of no credit losses. Accordingly, no allowance for credit losses has been recorded for these securities.

Regarding securities issued by state and political subdivisions and other HTM securities, the adequacy of the reserve for credit loss is determined quarterly based on methodology similar to the methodology for determining the allowance for credit losses on loans. The methodology considers, but is not limited to: (i) issuer bond ratings, (ii) issuer geography, (iii) whether issuers continue to make timely principal and interest payments under the contractual terms of the securities, (iv) probability-weighted multiple scenario forecasts, and (v) the issuers’ size.


(In thousands)	State and Political Subdivisions		Other Securities		Total
Three Months Ended June 30, 2023
Held-to-maturity
Beginning balance, April 1, 2023	$	362	$	1,526	$	1,888
Provision for credit loss expense	572		754		1,326
Ending balance, June 30, 2023	$	934	$	2,280	$	3,214

Available-for-sale
Beginning balance, April 1, 2023	$	—	$	5,800	$	5,800
Provision for credit loss expense	—		—		—
Reduction due to sales	—		(2,078)		(2,078)
Net increase (decrease) in allowance on previously impaired securities	—		(1,326)		(1,326)
Securities charged-off	—		—		—
Ending balance, June 30, 2023	$	—	$	2,396	$	2,396

Six Months Ended June 30, 2023
Held-to-maturity
Beginning balance, January 1, 2023	$	110	$	1,278	$	1,388
Provision for credit loss expense	824		1,002		1,826
Ending balance, June 30, 2023	$	934	$	2,280	$	3,214

Available-for-sale
Beginning balance, January 1, 2023	$	—	$	—	$	—
Provision for credit loss expense	—		12,800		12,800
Reduction due to sales	—		(2,078)		(2,078)
Net increase (decrease) in allowance on previously impaired securities	—		(1,326)		(1,326)
Securities charged-off	—		(7,000)		(7,000)
Ending balance, June 30, 2023	$	—	$	2,396	$	2,396


(In thousands)	State and Political Subdivisions		Other Securities		Total
Three Months Ended June 30, 2022
Held-to-maturity
Beginning balance, April 1, 2022	$	1,285	$	92	$	1,377
Provision for credit loss expense	—		—		—
Net increase (decrease) in allowance on previously impaired securities	(1,183)		1,183		—
Recoveries	1		3		4
Ending balance, June 30, 2022	$	103	$	1,278	$	1,381

Six Months Ended June 30, 2022
Held-to-maturity
Beginning balance, January 1, 2022	$	1,197	$	82	$	1,279
Provision for credit loss expense	—		—		—
Net increase (decrease) in allowance on previously impaired securities	(1,183)		1,183		—
Recoveries	89		13		102
Ending balance, June 30, 2022	$	103	$	1,278	$	1,381

Based upon the Company’s analysis of the underlying risk characteristics of its AFS portfolio, including credit ratings and other qualitative factors, as previously discussed, the provision for credit losses related to AFS securities recorded for the six months ended June 30, 2023 was $11.5 million, while the provision for credit losses related to AFS securities was reduced by $1.3 million during the three months ended June 30, 2023. During the six months ended June 30, 2023, the Company charged-off $7.0 million directly related to one corporate bond which was deemed uncollectible in the period. The remaining allowance for credit loss on the AFS portfolio of $2.4 million at June 30, 2023 is related to outstanding exposure for two nonperforming corporate bonds.


	State and Political Subdivisions
(In thousands)	Not Guaranteed or Pre-Refunded		Other Credit Enhancement or Insurance		Pre-Refunded		Total		Other Securities
Aaa/AAA	$	178,809	$	299,834	$	—	$	478,643	$	—
Aa/AA	638,308		522,367		—		1,160,675		—
A	47,154		161,399		—		208,553		101,965
Baa/BBB	—		4,371		—		4,371		153,192
Not Rated	7,714		—		—		7,714		—
Total	$	871,985	$	987,971	$	—	$	1,859,956	$	255,157

Historical loss rates associated with securities having similar grades as those in the Company’s portfolio have generally not been significant. Pre-refunded securities, if any, have been defeased by the issuer and are fully secured by cash and/or U.S. Treasury securities held in escrow for payment to holders when the underlying call dates of the securities are reached.


	Three Months Ended June 30,				Six Months Ended June 30,
(In thousands)	2023		2022		2023		2022
Taxable:
Held-to-maturity	$	11,058	$	10,578	$	22,071	$	12,490
Available-for-sale	21,687		11,217		43,478		27,453

Non-taxable:
Held-to-maturity	10,225		10,088		20,351		16,190
Available-for-sale	5,781		5,965		11,625		15,427
Total	$	48,751	$	37,848	$	97,525	$	71,560

The amortized cost and estimated fair value by maturity of securities as of June 30, 2023 are shown in the following table. Securities are classified according to their contractual maturities without consideration of principal amortization, potential prepayments or call options. Accordingly, actual maturities may differ from contractual maturities.


	Held-to-Maturity				Available-for-Sale
(In thousands)	Amortized Cost		Fair Value		Amortized Cost		Fair Value
One year or less	$	1,915	$	1,909	$	64,701	$	63,160
After one through five years	10,313		9,857		166,086		160,826
After five through ten years	363,981		315,452		218,164		187,975
After ten years	2,190,641		1,693,250		1,030,810		885,199
Securities not due on a single maturity date	1,193,118		1,074,390		2,532,234		2,282,328
Other securities (no maturity)	—		—		270		270
Total	$	3,759,968	$	3,094,858	$	4,012,265	$	3,579,758

There were no gross realized gains and $391,000 gross realized losses recorded from the sale of securities during both the three and six months ended June 30, 2023. There were no gross realized gains and approximately $150,000 of gross realized losses from the sale and calls of securities during the three months ended June 30, 2022, and approximately $37,000 of gross realized gains and $240,000 of gross realized losses from the sale and call of securities during the six months ended June 30, 2022. The income tax expense/benefit related to security gains/losses was 26.135% of the gross amounts in 2023 and 2022.

The Company has entered into various fair value hedging transactions to mitigate the impact of changing interest rates on the fair value of AFS securities. See Note 23, Derivative Instruments, for disclosure of the gains and losses recognized on derivative instruments and the cumulative fair value hedging adjustments to the carrying amount of the hedged securities.