
(dollars in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Allowance for Credit Losses		Estimated Fair Value
March 31, 2024
Investment securities available-for-sale:
U.S. treasury bonds	$	49,919	$	—	$	(1,686)	$	—	$	48,233
U.S. agency securities	698,189		—		(58,863)		—		639,326
Residential mortgage-backed securities	800,793		23		(102,266)		—		698,550
Commercial mortgage-backed securities	54,018		—		(5,080)		—		48,938
Municipal bonds	8,740		—		(434)		—		8,306
Corporate bonds	2,000		—		(302)		(17)		1,681

Total available-for-sale securities	$	1,613,659	$	23	$	(168,631)	$	(17)	$	1,445,034


(dollars in thousands)	Amortized Cost		Gross Unrecognized Gains		Gross Unrecognized Losses		Estimated Fair Value
March 31, 2024
Investment securities held-to-maturity:


Residential mortgage-backed securities	$	655,388	$	—	$	(87,348)	$	568,040
Commercial mortgage-backed securities	89,966		—		(13,000)		76,966
Municipal bonds	125,003		—		(9,789)		115,214
Corporate bonds	132,332		—		(14,393)		117,939

Total	$	1,002,689	$	—	$	(124,530)	$	878,159
Allowance for credit losses	(1,957)
Total held-to-maturity securities, net of ACL	$	1,000,732


(dollars in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Allowance for Credit Losses		Estimated Fair Value
December 31, 2023
Investment securities available-for-sale:
U.S. treasury bonds	$	49,894	$	—	$	(1,993)	$	—	$	47,901
U.S. agency securities	729,090		—		(57,693)		—		671,397
Residential mortgage-backed securities	823,992		45		(96,684)		—		727,353
Commercial mortgage-backed securities	54,557		—		(4,993)		—		49,564
Municipal bonds	8,783		—		(293)		—		8,490
Corporate bonds	2,000		—		(300)		(17)		1,683
Total available-for-sale securities	$	1,668,316	$	45	$	(161,956)	$	(17)	$	1,506,388


(dollars in thousands)	Amortized Cost		Gross Unrecognized Gains		Gross Unrecognized Losses		Estimated Fair Value
December 31, 2023
Investment securities held-to-maturity:


Residential mortgage-backed securities	$	670,043	$	—	$	(79,980)	$	590,063
Commercial mortgage-backed securities	90,227		—		(12,867)		77,360
Municipal bonds	125,114		5		(8,540)		116,579
Corporate bonds	132,309		—		(14,729)		117,580

Total	$	1,017,693	$	5	$	(116,116)	$	901,582
Allowance for credit losses	(1,956)
Total held-to-maturity securities, net of ACL	$	1,015,737

At March 31, 2024 and December 31, 2023, the Company held $54.7 million and $25.7 million, respectively, of equity securities in a combination of Federal Reserve System ("Federal Reserve Board," "Federal Reserve" or "FRB") and FHLB stocks, which are required to be held for regulatory purposes. The securities are not marketable, and therefore are carried at cost; they are classified as restricted securities, and periodically evaluated for impairment based on ultimate recovery of par value.

At March 31, 2024 and December 31, 2023, the Company had $50.0 million and $51.7 million, respectively, of unamortized unrealized losses outstanding following the transfer of investment securities from available-for-sale to held-to-maturity in 2022. These unrealized losses are included in accumulated other comprehensive loss and are amortized through interest income as a yield adjustment over the remaining term of the securities.

Accrued interest receivable on investment securities totaled $7.8 million and $7.6 million at March 31, 2024 and December 31, 2023, respectively. The accrued interest receivable is excluded from the amortized cost of the securities and is reported in other assets in the Consolidated Balance Sheets.


		Less Than 12 Months				12 Months or Greater				Total
(dollars in thousands)	Number of Securities	Estimated Fair Value		Unrealized Losses		Estimated Fair Value		Unrealized Losses		Estimated Fair Value		Unrealized Losses
March 31, 2024
Investment securities available-for-sale:
U.S. treasury bonds	2	$	—	$	—	$	48,233	$	(1,686)	$	48,233	$	(1,686)
U. S. agency securities	76	2,904		(5)		636,422		(58,858)		639,326		(58,863)
Residential mortgage-backed securities	151	8,180		(60)		688,525		(102,206)		696,705		(102,266)
Commercial mortgage-backed securities	13	—		—		48,938		(5,080)		48,938		(5,080)
Municipal bonds	1	—		—		8,306		(434)		8,306		(434)
Corporate bonds	1	—		—		1,681		(302)		1,681		(302)
Total	244	$	11,084	$	(65)	$	1,432,105	$	(168,566)	$	1,443,189	$	(168,631)


		Less Than 12 Months				12 Months or Greater				Total
(dollars in thousands)	Number of Securities	Estimated Fair Value		Unrecognized Losses		Estimated Fair Value		Unrecognized Losses		Estimated Fair Value		Unrecognized Losses
March 31, 2024
Investment securities held-to-maturity:
Residential mortgage-backed securities	142	$	—	$	—	$	568,040	$	(87,348)	$	568,040	$	(87,348)
Commercial mortgage-backed securities	16	—		—		76,966		(13,000)		76,966		(13,000)
Municipal bonds	42	3,474		(63)		111,740		(9,726)		115,214		(9,789)
Corporate bonds	30	—		—		105,887		(14,393)		105,887		(14,393)
Total	230	$	3,474	$	(63)	$	862,633	$	(124,467)	$	866,107	$	(124,530)


		Less Than 12 Months				12 Months or Greater				Total
(dollars in thousands)	Number of Securities	Estimated Fair Value		Unrealized Losses		Estimated Fair Value		Unrealized Losses		Estimated Fair Value		Unrealized Losses
December 31, 2023
Investment securities available-for-sale:
U.S. treasury bonds	2	$	—	$	—	$	47,901	$	(1,993)	$	47,901	$	(1,993)
U. S. agency securities	78	3,084		(4)		668,313		(57,689)		671,397		(57,693)
Residential mortgage-backed securities	149	—		—		718,042		(96,684)		718,042		(96,684)
Commercial mortgage-backed securities	13	—		—		49,564		(4,993)		49,564		(4,993)
Municipal bonds	1	—		—		8,490		(293)		8,490		(293)
Corporate bonds	1	—		—		1,683		(300)		1,683		(300)
Total	244	$	3,084	$	(4)	$	1,493,993	$	(161,952)	$	1,497,077	$	(161,956)


		Less Than 12 Months				12 Months or Greater				Total
(dollars in thousands)	Number of Securities	Estimated Fair Value		Unrecognized Losses		Estimated Fair Value		Unrecognized Losses		Estimated Fair Value		Unrecognized Losses
December 31, 2023
Investment securities held-to-maturity:
Residential mortgage-backed securities	142	$	—	$	—	$	590,063	$	(79,980)	$	590,063	$	(79,980)
Commercial mortgage-backed securities	16	—		—		77,360		(12,867)		77,360		(12,867)
Municipal bonds	40	—		—		113,031		(8,540)		113,031		(8,540)
Corporate bonds	30	—		—		105,523		(14,729)		105,523		(14,729)
Total	228	$	—	$	—	$	885,977	$	(116,116)	$	885,977	$	(116,116)

Unrealized losses at March 31, 2024 were generally attributable to changes in market interest rates and interest spread relationships subsequent to the dates the securities were originally purchased and were considered to be temporary, and not due to credit quality concerns on the investment securities. The fair values of these securities are expected to recover as the securities approach their respective maturity dates. The Company does not intend to sell and it is likely that it will not be required to sell the securities prior to their anticipated recovery.

The Company measures its AFS and HTM security portfolios for current expected credit losses as part of its ACL analysis. During the three months ended March 31, 2024 and 2023, the Company recorded a provision for credit losses on its held-to-maturity portfolio of $1 thousand and $1.2 million, respectively. During the three months ended March 31, 2023, the Company recorded a provision for credit losses on its available-for-sale portfolio of $14 thousand. No provision was recorded for its available-for-sale security portfolio during the three months ended March 31, 2024. At March 31, 2024 and December 31, 2023, the Company had a total allowance of $17 thousand on its available-for-sale securities and $2.0 million on its held-to-maturity securities, each of which primarily comprise allowances for corporate bonds.

The following table summarizes the Company's investment securities available-for-sale and investment securities held-to-maturity by contractual maturity. Expected maturities for mortgage-backed securities ("MBS") will differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties.


	March 31, 2024
(dollars in thousands)	Amortized Cost		Estimated Fair Value
Investment securities available-for-sale:
Within one year	$	139,224	$	135,426
One to five years	486,394		446,955
Five to ten years	112,838		97,570
Beyond ten years	20,392		17,612
Residential mortgage-backed securities	800,793		698,550
Commercial mortgage-backed securities	54,018		48,938

Less: allowance for credit losses	—		(17)
Total investment securities available-for-sale	1,613,659		1,445,034

Investment securities held-to-maturity:
Within one year	4,282		4,247
One to five years	61,707		59,309
Five to ten years	117,237		102,274
Beyond ten years	74,109		67,323
Residential mortgage-backed securities:	655,388		568,040
Commercial mortgage-backed securities	89,966		76,966

Less: allowance for credit losses	(1,957)		—
Total investment securities held-to-maturity	1,000,732		878,159
Total	$	2,614,391	$	2,323,193

There were no gross realized losses on sales or calls of investment securities during the three months ended March 31, 2024. During the three months ended March 31, 2023, there were $26 thousand of gross realized losses on sales or calls of investment securities.

The book value of securities pledged as collateral for certain government deposits, securities sold under agreements to repurchase, and certain lines of credit with correspondent banks at March 31, 2024 and December 31, 2023 was $2.1 billion, which were well in excess of required amounts in order to operationally provide significant reserve amounts for new business. As of March 31, 2024 and December 31, 2023, there were no holdings of securities of any one issuer, other than the U.S. Government and U.S. agency securities, which exceeded ten percent of shareholders' equity.