The following tables detail the amortized cost, allowance for credit losses and the estimated fair value of the Company's investments in available-for-sale and held-to-maturity debt securities. None of the Company's investments in debt securities are classified as trading.


	September 30, 2022
(Dollars in thousands)	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss		Allowance for Credit Losses		Fair Value
Available-for-Sale Debt Securities
Collateralized mortgage obligation (CMO)	$	621,673	$	—	$	99,290	$	—	$	522,383
Fannie Mae (FNMA) mortgage-backed securities (MBS)	3,911,290		—		617,060		—		3,294,230
Freddie Mac (FHLMC) MBS	138,391		—		15,374		—		123,017
Ginnie Mae (GNMA) MBS	40,100		—		3,363		—		36,737
Government-sponsored enterprises (GSE) agency notes	228,653		—		51,405		—		177,248
	$	4,940,107	$	—	$	786,492	$	—	$	4,153,615
Held-to-Maturity Debt Securities(1)
FNMA MBS	$	919,383	$	—	$	69,694	$	—	$	849,689
State and political subdivisions	202,022		2		11,039		10		190,975
Foreign bonds	500		—		1		—		499
	$	1,121,905	$	2	$	80,734	$	10	$	1,041,163

(1)Held-to-maturity securities transferred from available-for-sale are included in held-to-maturity at fair value basis at the time of transfer. The amortized cost of transferred held-to-maturity securities included net unrealized losses of $149.6 million at September 30, 2022, which are offset in Accumulated other comprehensive (loss) income. At the time of transfer, there was no allowance for credit loss on the available-for-sale securities. Subsequent to transfer, the securities were evaluated for credit loss.


	December 31, 2021
(Dollars in thousands)	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss		Allowance for Credit Losses		Fair Value
Available-for-Sale Debt Securities
CMO	$	586,830	$	3,569	$	14,633	$	—	$	575,766
FNMA MBS	4,275,307		24,170		53,793		—		4,245,684
FHLMC MBS	139,708		6,336		516		—		145,528
GNMA MBS	17,456		551		71		—		17,936
GSE agency notes	230,581		—		10,184		—		220,397
	$	5,249,882	$	34,626	$	79,197	$	—	$	5,205,311
Held-to-Maturity Debt Securities(1)
State and political subdivisions	$	90,146	$	3,489	$	—	$	4	$	93,631
Foreign bonds	500		—		—		—		500
	$	90,646	$	3,489	$	—	$	4	$	94,131

(1)Held-to–maturity securities transferred from available-for-sale are included in held-to-maturity at fair value at the time of transfer. The amortized cost of transferred held-to-maturity securities included net unrealized gains of $0.2 million at December 31, 2021, which are offset in Accumulated other comprehensive income. At the time of transfer, there was no allowance for credit loss on the available-for-sale securities. Subsequent to transfer, the securities were evaluated for credit loss.

The scheduled maturities of available-for-sale debt securities at September 30, 2022 and December 31, 2021 are presented in the table below:


	Available-for-Sale
	Amortized		Fair
(Dollars in thousands)	Cost		Value
September 30, 2022 (1)
Within one year	$	1,501	$	1,498
After one year but within five years	86,119		80,366
After five years but within ten years	457,657		390,595
After ten years	4,394,830		3,681,156
	$	4,940,107	$	4,153,615
December 31, 2021 (1)
Within one year	$	—	$	—
After one year but within five years	103,960		107,009
After five years but within ten years	204,186		204,289
After ten years	4,941,736		4,894,013
	$	5,249,882	$	5,205,311

As of September 30, 2022, substantially all of the Corporation’s available-for-sale investment securities were mortgage-backed securities or collateral mortgage obligations which were issued or guaranteed by U.S. government-sponsored entities and agencies.

As of September 30, 2022 and December 31, 2021, there were no holdings of securities of any one issuer, other than the U.S. government and its agencies, in an amount greater than 10% of shareholders’ equity.

The scheduled maturities of held-to-maturity debt securities at September 30, 2022 and December 31, 2021 are presented in the table below:


	Held-to-Maturity
	Amortized		Fair
(Dollars in thousands)	Cost		Value
September 30, 2022 (1)
Within one year	$	732	$	729
After one year but within five years	7,393		7,233
After five years but within ten years	46,097		44,859
After ten years	1,067,683		988,342
	$	1,121,905	$	1,041,163
December 31, 2021 (1)
Within one year	$	232	$	234
After one year but within five years	2,675		2,736
After five years but within ten years	44,137		45,404
After ten years	43,602		45,757
	$	90,646	$	94,131

MBS may have expected maturities that differ from their contractual maturities. These differences arise because issuers may have the right to call securities and borrowers may have the right to prepay obligations with or without prepayment penalty. The estimated weighted average duration of MBS was 6.0 years at September 30, 2022.

The held-to-maturity debt securities are not collateral-dependent securities as these are general obligation bonds issued by cities, states, counties, or other local and foreign governments.

During the second quarter of 2022, the Company transferred investment securities with a book value of $1.1 billion from available-for-sale to held-to-maturity to mitigate the impact of the rising interest rate environment to Accumulated other comprehensive (loss) income in the Company's Consolidated Statement of Changes in Stockholders' Equity. The transfer occurred at a fair value totaling $931.4 million. The amortized cost of transferred held-to-maturity securities included net unrealized losses of $157.6 million at June 30, 2022, which are offset in Accumulated other comprehensive (loss) income. No gains or losses on these securities were recognized at the time of transfer.

Investment securities with fair market values aggregating $2.9 billion and $2.2 billion were pledged as collateral for retail customer repurchase agreements, municipal deposits, and other obligations as of September 30, 2022 and December 31, 2021, respectively.

During the nine months ended September 30, 2022, the Company had no sales of debt securities categorized as available-for-sale. During the nine months ended September 30, 2021, the Company sold $14.0 million of debt securities categorized as available-for-sale resulting in $0.3 million of realized gains and no realized losses.

As of September 30, 2022 and December 31, 2021, the Company's debt securities portfolio had remaining unamortized premiums of $69.2 million and $69.4 million, respectively, and unaccreted discounts of $26.4 million and $12.7 million, respectively.

For debt securities in an unrealized loss position, the table below shows the gross unrealized losses and fair value by investment category and length of time that individual debt securities were in a continuous unrealized loss position at September 30, 2022.


	Duration of Unrealized Loss Position
	Less than 12 months				12 months or longer				Total
	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
(Dollars in thousands)	Value		Loss		Value		Loss		Value		Loss
Available-for-sale debt securities:
CMO	$	199,644	$	20,982	$	322,739	$	78,308	$	522,383	$	99,290
FNMA MBS	2,232,612		369,840		1,061,618		247,220		3,294,230		617,060
FHLMC MBS	101,605		12,968		8,036		2,406		109,641		15,374
GNMA MBS	34,985		2,936		1,751		427		36,736		3,363
GSE agency notes	—		—		177,248		51,405		177,248		51,405
	$	2,568,846	$	406,726	$	1,571,392	$	379,766	$	4,140,238	$	786,492

Held-to-maturity debt securities:
FNMA MBS	$	849,689	$	69,694	$	—	$	—	$	849,689	$	69,694
State and political subdivisions	183,181		11,039		—		—		183,181		11,039
Foreign bonds	500		1		—		—		500		1
	$	1,033,370	$	80,734	$	—	$	—	$	1,033,370	$	80,734


	Duration of Unrealized Loss Position
	Less than 12 months				12 months or longer				Total
	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
(Dollars in thousands)	Value		Loss		Value		Loss		Value		Loss
Available-for-sale debt securities:
CMO	$	411,347	$	12,730	$	35,638	$	1,903	$	446,985	$	14,633
FNMA MBS	3,018,606		41,021		356,665		12,772		3,375,271		53,793
FHLMC MBS	11,227		348		1,917		168		13,144		516
GNMA MBS	4,847		71		—		—		4,847		71
GSE agency notes	64,509		1,918		155,888		8,266		220,397		10,184
	$	3,510,536	$	56,088	$	550,108	$	23,109	$	4,060,644	$	79,197

At September 30, 2022, debt securities for which the amortized cost basis exceeded fair value totaled $5.2 billion. Total unrealized losses on these securities were $867.2 million at September 30, 2022. The Company does not have the intent to sell, nor is it more likely than not it will be required to sell these securities before it is able to recover the amortized cost basis. The unrealized losses are the result of changes in market interest rates subsequent to purchase, not credit loss, as these are highly rated agency securities with no expected credit loss, in the event of a default. As a result, there is no allowance for credit losses recorded for available-for-sale debt securities as of September 30, 2022.

At September 30, 2022 and December 31, 2021, held-to-maturity debt securities had an amortized cost basis of $1.1 billion and $90.6 million, respectively. The held-to-maturity debt security portfolio primarily consists of mortgage-backed securities which were issued or guaranteed by U.S. government-sponsored entities and agencies and highly rated municipal bonds. The Company monitors credit quality of its debt securities through credit ratings. The following table summarizes the amortized cost of debt securities held-to-maturity as of September 30, 2022, aggregated by credit quality indicator:


(Dollars in thousands)	FNMA MBS		State and political subdivisions		Foreign bonds
A+ rated or higher	$	—	$	202,022	$	500
Not rated	919,383		—		—
Ending balance	$	919,383	$	202,022	$	500

The Company reviewed its held-to-maturity debt securities by major security type for potential credit losses. There was no activity in the allowance for credit losses for FNMA MBS and foreign bond debt securities for the nine months ended September 30, 2022 and 2021. The following table presents the activity in the allowance for credit losses for state and political subdivisions debt securities for the three and nine months ended September 30, 2022 and 2021:


	Three months ended September 30,				Nine months ended September 30,
(Dollars in thousands)	2022		2021		2022		2021
Allowance for credit losses:
Beginning balance	$	6	$	5	$	4	$	6

Provision for credit losses	4		(1)		6		(2)



Ending balance	$	10	$	4	$	10	$	4

Accrued interest receivable of $1.8 million and $0.9 million as of September 30, 2022 and December 31, 2021, respectively, for held-to-maturity debt securities were excluded from the evaluation of allowance for credit losses. There were no nonaccrual or past due held-to-maturity debt securities as of September 30, 2022 and December 31, 2021.

During the nine months ended September 30, 2022, total net gains on equity investments of $6.0 million were recorded, driven by an unrealized gain on the Company's investment in CRED.ai presented within Unrealized gain on equity investment, net in the Consolidated Statements of Income.