
(Dollars in thousands)	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss		Estimated Fair Value
Investment securities available-for-sale:
December 31, 2021
U.S. Treasury	$	57,708	$	614	$	(456)	$	57,866
Agency	440,183		2,081		(10,129)		432,135
Corporate	451,621		6,096		(3,856)		453,861
Municipal bonds	1,061,985		32,209		(4,281)		1,089,913
Collateralized mortgage obligations	680,686		2,012		(6,055)		676,643
Mortgage-backed securities	1,586,406		3,220		(26,180)		1,563,446
Total investment securities available-for-sale	$	4,278,589	$	46,232	$	(50,957)	$	4,273,864

December 31, 2020
U.S. Treasury	$	30,153	$	2,380	$	—	$	32,533
Agency	666,702		24,292		(608)		690,386
Corporate	412,223		3,591		(506)		415,308
Municipal bonds	1,412,012		37,260		(3,253)		1,446,019
Collateralized mortgage obligations	513,259		819		(712)		513,366
Mortgage-backed securities	812,384		21,662		(543)		833,503
Total investment securities available-for-sale	$	3,846,733	$	90,004	$	(5,622)	$	3,931,115


(Dollars in thousands)	Amortized Cost		Allowance for Credit Losses		Net Carrying Amount		Gross Unrecognized Gain		Gross Unrecognized Loss		Estimated Fair Value
Investment securities held-to-maturity:
December 31, 2021
Municipal bonds	$	368,344	$	(22)	$	368,322	$	3,834	$	(1,649)	$	370,507
Mortgage-backed securities	11,843		—		11,843		564		—		12,407
Other	1,509		—		1,509		—		—		1,509
Total investment securities held-to-maturity	$	381,696	$	(22)	$	381,674	$	4,398	$	(1,649)	$	384,423

December 31, 2020

Mortgage-backed securities	$	22,124	$	—	$	22,124	$	1,281	$	—	$	23,405
Other	1,608		—		1,608		—		—		1,608
Total investment securities held-to-maturity	$	23,732	$	—	$	23,732	$	1,281	$	—	$	25,013

The Company reassesses classification of certain investments as part of the ongoing review of the investment securities portfolio. During the year, the Company transferred approximately $326.5 million of municipal bonds, which the Company intends and has the ability to hold to maturity, from available-for sale to held-to-maturity securities. The transfer of these securities was accounted for at fair value. These securities had a net carrying amount of $319.9 million with a pre-tax unrealized loss of $6.6 million, which was reflected as a discount on the date of transfer. This discount, as well as the related unrealized loss in accumulated other comprehensive income, is amortized into interest income as a yield adjustment over the remaining term of the securities. The amortization of the unrealized loss reported in accumulated other comprehensive income offsets the effect on interest income of the amortization of the discount. No gains or losses were recorded at the time of transfer.

Unrealized gains and losses on investment securities available-for-sale are recognized in stockholders’ equity as accumulated other comprehensive income or loss. At December 31, 2021, the Company had accumulated other comprehensive loss of $4.7 million, or $3.3 million net of tax, compared to accumulated other comprehensive income of $84.4 million, or $60.3 million net of tax, at December 31, 2020.

For investment securities transferred from available-for-sale to held-to-maturity, the unrealized gains and losses at the date of transfer continue to be reported in stockholders’ equity as accumulated other comprehensive income and are amortized over the remaining lives of the securities with an offsetting entry to interest income as an adjustment of yield. At December 31, 2021, the gross unrealized loss on municipal bonds transferred from available-for-sale to held-to-maturity in accumulated other comprehensive loss was $6.3 million, or $4.5 million net of tax.

The table below shows the number, fair value, and gross unrealized holding losses of the Company’s investment securities available-for-sale in an unrealized loss position for which an allowance for credit losses has not been recorded as of the dates indicated, aggregated by investment category and length of time in a continuous loss position.


	December 31, 2021
	Less than 12 months					12 months or Longer					Total
(Dollars in thousands)	Number	Fair Value		Gross Unrealized Losses		Number	Fair Value		Gross Unrealized Losses		Number	Fair Value		Gross Unrealized Losses
Investment securities available-for-sale:
U.S. Treasury	3	$	47,235	$	(456)	—	$	—	$	—	3	$	47,235	$	(456)
Agency	19	278,078		(5,634)		16	119,750		(4,495)		35	397,828		(10,129)
Corporate	17	166,563		(849)		3	57,274		(3,007)		20	223,837		(3,856)
Municipal bonds	36	277,564		(4,079)		2	6,596		(202)		38	284,160		(4,281)
Collateralized mortgage obligations	26	226,763		(3,738)		15	121,185		(2,317)		41	347,948		(6,055)
Mortgage-backed securities	103	1,306,455		(20,417)		15	173,121		(5,763)		118	1,479,576		(26,180)
Total investment securities available-for-sale	204	$	2,302,658	$	(35,173)	51	$	477,926	$	(15,784)	255	$	2,780,584	$	(50,957)


	December 31, 2020
	Less than 12 months					12 months or Longer					Total
(Dollars in thousands)	Number	Fair Value		Gross Unrealized Losses		Number	Fair Value		Gross Unrealized Losses		Number	Fair Value		Gross Unrealized Losses
Investment securities available-for-sale:

Agency	4	$	74,194	$	(307)	9	$	10,434	$	(301)	13	$	84,628	$	(608)
Corporate	9	71,226		(506)		—	—		—		9	71,226		(506)
Municipal bonds	56	312,894		(3,253)		—	—		—		56	312,894		(3,253)
Collateralized mortgage obligations	21	215,603		(710)		1	431		(2)		22	216,034		(712)
Mortgage-backed securities	16	139,071		(543)		—	—		—		16	139,071		(543)
Total investment securities available-for-sale	106	$	812,988	$	(5,319)	10	$	10,865	$	(303)	116	$	823,853	$	(5,622)

The Company reviews individual securities classified as available-for-sale to determine whether a decline in fair value below the amortized cost basis is deemed credit related or due to other factors such as changes in interest rates and general market conditions. An ACL on available-for-sale investment securities is recorded when the fair value of the investment is below its amortized cost and the decline in fair value has been deemed, through the Company’s qualitative assessment, to be credit related. Non-credit related declines in fair value of available-for-sale investment securities, which may be attributed to changes in interest rates and other market related factors, are not recorded through an ACL. Such declines are recorded as an adjustment to accumulated other comprehensive income, net of tax. In the event the Company is required to sell or has the intent to sell an available-for-sale security that has experienced a decline in fair value below its amortized cost, the Company writes the amortized cost of the security down to fair value in the current period.

Credit losses on held-to-maturity investment securities are recorded at the time of purchase or acquisition and when the Company has designated securities as held-to-maturity. Credit losses on held-to-maturity investment securities are representative of current expected credit losses that may be incurred over the life of the investment.

The Company determines credit losses on both available-for-sale and held-to-maturity investment securities through the use of a discounted cash flow approach using the security’s effective interest rate. The ACL is measured as the amount by which an investment security’s amortized cost exceeds the net present value of expected future cash flows. However, the amount of credit losses for available-for-sale investment securities is limited to the amount of a security’s unrealized loss. The ACL is established through a charge to provision for credit losses in current period earnings.

During the second quarter of 2020, the Company acquired $829.9 million of available-for-sale securities in connection with the acquisition of Opus. Such securities were evaluated and it was determined that there were no investment securities classified as purchase credit deteriorated upon acquisition and, as a result, no allowance for credit losses was recorded.

At December 31, 2021, the Company had an ACL of $22,000 for held-to-maturity investment securities classified as municipal bonds, which primarily consisted of the securities transferred from available-for-sale during the third and fourth quarters of 2021. There was no ACL for held-to-maturity investment securities at December 31, 2020. The Company recognized $22,000 of provision for credit losses for held-to-maturity investment securities during the year ended December 31, 2021. There was no provision for credit losses recognized for held-to-maturity investment securities during the year ended December 31, 2020.

The Company had no ACL for available-for-sale or investment securities at December 31, 2021 and 2020. As of December 31, 2021 the Company has not recorded credit losses on certain available-for-sale securities that were in an unrealized loss position due to the high quality of the investments, with investment grade ratings, and many of them are issued by U.S. government agencies. Additionally, the Company continues to receive contractual principal and interest payments in a timely manner. The Company performed a qualitative assessment of these investments as of December 31, 2021, and does not believe the declines in fair value were credit related. There were no provision for credit losses recognized for investment securities during the year ended December 31, 2021 and 2020. There were no other than temporary impairment losses recognized for investment securities for the year ended December 31, 2019.

At December 31, 2021 and 2020, there were no available-for-sale or held-to-maturity securities in nonaccrual status. All securities in the portfolio were current with their contractual principal and interest payments. At December 31, 2021 and 2020, there were no securities purchased with deterioration in credit quality since their origination. At December 31, 2021 and 2020, there were no collateral dependent available-for-sale or held-to-maturity securities.


	Vintage
(Dollars in thousands)	2021		2020		2019		2018		2017		Prior		Total
Investment securities available-for-sale at fair value:
U.S. Treasury
Aaa - Aa3	$	32,727	$	14,508	$	—	$	10,631	$	—	$	—	$	57,866


Agency
Aaa - Aa3	24,216		296,403		26,017		59,931		—		12,538		419,105

Baa1 - Baa3	—		—		—		5,410		—		7,620		13,030
Corporate debt

A1 - A3	136,607		67,326		—		—		17,938		—		221,871
Baa1 - Baa3	46,492		100,709		71,242		—		—		13,547		231,990
Municipal bonds
Aaa - Aa3	118,922		563,238		291,483		32,483		50,149		32,780		1,089,055
A1 - A3	—		—		—		—		—		858		858

Collateralized mortgage obligations
Aaa - Aa3	268,693		207,155		75,834		16,710		13,274		94,977		676,643


Mortgage-backed securities
Aaa - Aa3	1,109,054		358,114		68,606		—		19,777		7,895		1,563,446


Total investment securities available-for-sale	$	1,736,711	$	1,607,453	$	533,182	$	125,165	$	101,138	$	170,215	$	4,273,864


	Vintage
(Dollars in thousands)	2021		2020		2019		2018		2017		Prior		Total
Investment securities held-to-maturity at amortized cost:
Municipal bonds
Aaa - Aa3	$	48,540	$	319,804	$	—	$	—	$	—	$	—	$	368,344


Mortgage-backed securities
Aaa - Aa3	—		—		—		3,425		3,325		5,093		11,843


Other


Baa1 - Baa3	—		—		—		591		—		918		1,509
Total investment securities held-to-maturity	48,540		319,804		—		4,016		3,325		6,011		381,696
Total investment securities	$	1,785,251	$	1,927,257	$	533,182	$	129,181	$	104,463	$	176,226	$	4,655,560

During the years ended December 31, 2021, 2020, and 2019, the Company recognized gross realized gains on sales of available-for-sale securities in the amounts of $23.2 million, $15.7 million, and $10.3 million, respectively. During the years ended December 31, 2021, 2020, and 2019, the Company recognized gross realized losses on sales of available-for-sale securities in the amounts of $6.3 million, $1.8 million, and $1.8 million, respectively. The Company had net proceeds from the sale of available-for-sale securities of $901.1 million, $766.5 million, and $551.8 million during the years ended December 31, 2021, 2020, and 2019, respectively.


	Due in One Year or Less				Due after One Year through Five Years				Due after Five Years through Ten Years				Due after Ten Years				Total
(Dollars in thousands)	Amortized Cost		Fair Value		Amortized Cost		Fair Value		Amortized Cost		Fair Value		Amortized Cost		Fair Value		Amortized Cost		Fair Value
Investment securities available-for-sale:
Treasury	$	—	$	—	$	10,017	$	10,631	$	47,691	$	47,235	$	—	$	—	$	57,708	$	57,866
Agency	—		—		298,491		294,580		97,882		95,525		43,810		42,030		440,183		432,135
Corporate	—		—		61,302		61,154		390,319		392,707		—		—		451,621		453,861
Municipal bonds	—		—		3,129		3,289		90,884		91,329		967,972		995,295		1,061,985		1,089,913
Collateralized mortgage obligations	—		—		32,960		32,900		215,306		211,057		432,420		432,686		680,686		676,643
Mortgage-backed securities	—		—		2,074		2,156		629,678		624,990		954,654		936,300		1,586,406		1,563,446
Total investment securities available-for-sale	—		—		407,973		404,710		1,471,760		1,462,843		2,398,856		2,406,311		4,278,589		4,273,864
Investment securities held-to-maturity:
Municipal bonds	—		—		—		—		—		—		368,344		370,507		368,344		370,507
Mortgage-backed securities	—		—		—		—		—		—		11,843		12,407		11,843		12,407
Other	—		—		—		—		—		—		1,509		1,509		1,509		1,509
Total investment securities held-to-maturity	—		—		—		—		—		—		381,696		384,423		381,696		384,423
Total investment securities	$	—	$	—	$	407,973	$	404,710	$	1,471,760	$	1,462,843	$	2,780,552	$	2,790,734	$	4,660,285	$	4,658,287

The Company’s equity securities primarily consist of FHLB and FRB stock, which are considered restricted securities and held as a condition of membership of the FHLB and the Board of Governors of the Federal Reserve System. These equity securities without readily determinable fair values are carried at cost less impairment. At December 31, 2021, the Company had $17.3 million in FHLB stock, $74.5 million in FRB stock, and $25.7 million in other stock, all carried at cost. During the year ended December 31, 2021, FHLB did not repurchase any of the Company’s excess FHLB stock through its stock repurchase program. During the year ended December 31, 2020 and 2019, FHLB had repurchased $17.3 million and $18.3 million, respectively, of the Company’s excess FHLB stock through their stock repurchase program.