Held-to-maturity (“HTM”) securities, which include any security for which the Company has 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 (“AFS”) securities, 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 third quarter of 2021, the Company transferred, at fair value, $500.8 million of securities from the AFS portfolio to the HTM portfolio. The related net unrealized gains of $1.0 million remained in accumulated other comprehensive income (loss) at December 31, 2021 and 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

December 31, 2021
U.S. Government agencies	232,609		—		232,609		—		(7,914)		224,695
Mortgage-backed securities	$	70,342	$	—	$	70,342	$	232	$	(1,425)	$	69,149
State and political subdivisions	1,210,248		(1,197)		1,209,051		6,166		(8,462)		1,206,755
Other securities	17,301		(82)		17,219		—		(440)		16,779
Total HTM	$	1,530,500	$	(1,279)	$	1,529,221	$	6,398	$	(18,241)	$	1,517,378

December 31, 2020
Mortgage-backed securities	22,354		—		22,354		683		—		23,037
State and political subdivisions	$	312,416	$	(2,307)	$	310,109	$	8,148	$	(30)	$	318,227
Other securities	1,176		(608)		568		93		—		661
Total HTM	$	335,946	$	(2,915)	$	333,031	$	8,924	$	(30)	$	341,925

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 December 31, 2021, HTM MBS consisted of $4.9 million and $65.5 million of commercial MBS and residential MBS, respectively. As of December 31, 2020, HTM MBS consisted of $7.7 million and $14.7 million 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

December 31, 2021
U.S. Treasury	300		—		—		—		300
U.S. Government agencies	$	374,754	$	—	$	495	$	(10,608)	$	364,641
Mortgage-backed securities	4,485,548		—		6,307		(43,239)		4,448,616
State and political subdivisions	1,791,097		—		30,556		(1,995)		1,819,658
Other securities	479,162		—		6,647		(5,479)		480,330
Total AFS	$	7,130,861	$	—	$	44,005	$	(61,321)	$	7,113,545

December 31, 2020
U.S. Government agencies	$	477,693	$	—	$	844	$	(1,300)	$	477,237
Mortgage-backed securities	1,374,769		—		21,261		(1,094)		1,394,936
State and political subdivisions	1,416,136		(217)		55,111		(307)		1,470,723
Other securities	128,445		(95)		2,447		(95)		130,702
Total AFS	$	3,397,043	$	(312)	$	79,663	$	(2,796)	$	3,473,598

All mortgage-backed securities included in the table above were issued by U.S. government agencies or corporations. As of December 31, 2021, AFS MBS consisted of $1.53 billion and $2.92 billion of commercial MBS and residential MBS, respectively. As of December 31, 2020, AFS MBS consisted of $406.1 million and $988.8 million of commercial MBS and residential MBS, respectively.

Accrued interest receivable on HTM and AFS securities at December 31, 2021 was $9.7 million and $23.4 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 December 31, 2021, 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. Government agencies	$	152,908	$	(3,297)	$	160,913	$	(7,311)	$	313,821	$	(10,608)
Mortgage-backed securities	3,632,822		(33,551)		323,683		(9,688)		3,956,505		(43,239)
State and political subdivisions	530,647		(709)		29,565		(1,286)		560,212		(1,995)
Other securities	228,182		(5,240)		6,984		(239)		235,166		(5,479)
Total AFS	$	4,544,559	$	(42,797)	$	521,145	$	(18,524)	$	5,065,704	$	(61,321)

As of December 31, 2021, the Company’s investment portfolio included $7.11 billion of AFS securities, of which $5.07 billion, or 71.2%, were in an unrealized loss position that are not deemed to have credit losses. A portion of the unrealized losses were related to the Company’s mortgage-backed securities, which are issued and guaranteed by U.S. government-sponsored entities and agencies, and the Company’s state and political 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

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, are 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, management considers (i) issuer bond ratings, (ii) historical loss rates for given bond ratings, (iii) whether issuers continue to make timely principal and interest payments under the contractual terms of the securities, (iv) internal forecasts, (v) whether or not such securities provide insurance or other credit enhancement or are pre-refunded by the issuers.


(In thousands)	State and Political Subdivisions		Other Securities		Total
December 31, 2021

Held-to-maturity
Beginning balance, January 1, 2021	$	2,307	$	608	$	2,915
Provision for credit loss expense	(1,110)		(73)		(1,183)
Securities charged-off	—		(600)		(600)
Recoveries	—		147		147
Ending balance, December 31, 2021	$	1,197	$	82	$	1,279

Available-for-sale
Beginning balance, January 1, 2021	$	217	$	95	$	312
Reduction due to sales	—		(11)		(11)
Net decrease in allowance on previously impaired securities	(217)		(84)		(301)
Ending balance, December 31, 2021	$	—	$	—	$	—

December 31, 2020
Held-to-maturity
Beginning balance, January 1, 2020	$	—	$	—	$	—
Impact of ASU 2016-13 adoption	58		311		369
Provision for credit loss expense	2,249		297		2,546
Ending balance, December 31, 2020	$	2,307	$	608	$	2,915

Available-for-sale
Beginning balance, January 1, 2020	$	—	$	—	$	—
Impact of ASU 2016-13 adoption	373		—		373
Credit losses on securities not previously recorded	199		113		312
Reduction due to sales	(244)		—		(244)
Net decrease in allowance on previously impaired securities	(111)		(18)		(129)
Ending balance, December 31, 2020	$	217	$	95	$	312

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, there was no provision for credit losses related to AFS securities recorded in the last half of 2021. During the year ended December 31, 2021 and 2020, the provision for credit losses was reduced by $312,000 and $61,000, respectively, related to AFS securities.


	State and Political Subdivisions
(In thousands)	Not Guaranteed or Pre-Refunded		Other Credit Enhancement or Insurance		Pre-Refunded		Total		Other Securities
Aaa/AAA	$	129,473	$	102,712	$	—	$	232,185	$	—
Aa/AA	481,887		316,345		—		798,232		—
A	42,727		89,643		—		132,370		—
Baa/BBB	—		13,539				13,539
Not Rated	6,207		27,715		—		33,922		17,301
Total	$	660,294	$	549,954	$	—	$	1,210,248	$	17,301

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. Securities with other credit enhancement or insurance continue to make timely principal and interest payments under the contractual terms of the securities. Accordingly, no allowance for credit losses has been recorded for these securities as there is no current expectation of credit losses related to these securities.


(In thousands)	2021		2020		2019
Taxable:
Held-to-maturity	$	4,208	$	985	$	1,207
Available-for-sale	54,768		34,054		42,412

Non-taxable:
Held-to-maturity	16,047		919		1,412
Available-for-sale	36,670		28,575		18,345
Total	$	111,693	$	64,533	$	63,376

The amortized cost and estimated fair value by maturity of securities are shown in the following table as of December 31, 2021. 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	$	5,333	$	5,396	$	7,821	$	7,845
After one through five years	4,801		5,023		61,456		61,669
After five through ten years	27,081		25,874		532,085		533,711
After ten years	1,422,943		1,411,936		2,043,326		2,061,081
Securities not due on a single maturity date	70,342		69,149		4,485,547		4,448,615
Other securities (no maturity)	—		—		626		624
Total	$	1,530,500	$	1,517,378	$	7,130,861	$	7,113,545

The Company sold approximately $342.6 million of investment securities compared to approximately $1.7 billion of investment securities during 2021 and 2020, respectively. The increase in securities sold in 2020 was in large part related to efforts by the Company to increase liquidity in response to the early stages of the COVID-19 pandemic. There were approximately $15.9 million of gross realized gains and $422,000 of gross realized losses from the sale of securities during the year ended December 31, 2021. There were approximately $54.8 million of gross realized gains and $15,000 of gross realized losses from the sale of securities during the year ended December 31, 2020. There were approximately $13.3 million of gross realized gains and $4,000 of gross realized losses from the sale of securities during the year ended December 31, 2019. The income tax expense/benefit related to security gains/losses was 26.135% of the gross amounts in 2021, 2020 and 2019.

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 21: 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.