
	March 31, 2021
	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss		Estimated Fair Value
	(Dollars in thousands)
Investment securities available-for-sale:
U.S. Treasury	$	30,144	$	1,919	$	—	$	32,063
Agency	660,582		12,956		(10,379)		663,159
Corporate	360,617		2,128		(4,911)		357,834
Municipal bonds	1,432,169		22,287		(32,394)		1,422,062
Collateralized mortgage obligations	514,250		431		(5,710)		508,971
Mortgage-backed securities	880,903		9,309		(16,964)		873,248
Total investment securities available-for-sale	3,878,665		49,030		(70,358)		3,857,337
Investment securities held-to-maturity:
Mortgage-backed securities	20,353		1,073		—		21,426
Other	1,578		—		—		1,578
Total investment securities held-to-maturity	21,931		1,073		—		23,004
Total investment securities	$	3,900,596	$	50,103	$	(70,358)	$	3,880,341


	December 31, 2020
	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss		Estimated Fair Value
	(Dollars in thousands)
Investment securities available-for-sale:
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
Investment securities held-to-maturity:
Mortgage-backed securities	22,124		1,281		—		23,405
Other	1,608		—		—		1,608
Total investment securities held-to-maturity	23,732		1,281		—		25,013
Total investment securities	$	3,870,465	$	91,285	$	(5,622)	$	3,956,128

Unrealized gains and losses on investment securities available-for-sale are recognized in stockholders’ equity as accumulated other comprehensive income or loss. At March 31, 2021, the Company had accumulated other comprehensive loss of $21.3 million, or $15.2 million net of tax, compared to an accumulated other comprehensive income of $84.4 million, or $60.3 million net of tax, at December 31, 2020.

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. The Company recognizes credit losses in current period earnings, through a change to provision for credit losses, when declines in the fair value of individual available-for-sale securities are below their amortized cost, and the decline in fair value is deemed to be credit related. Declines in fair value below amortized cost not deemed credit related are recorded net of tax in accumulated other comprehensive income. 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.

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.

As of March 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 March 31, 2021, and does not believe the declines in fair value are credit related. There was no provision for credit losses recognized for investment securities during the three months ended March 31, 2021, December 31, 2020, and March 31, 2020.

At March 31, 2021 and December 31, 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 March 31, 2021 and December 31, 2020, there were no securities purchased with deterioration in credit quality since their origination. At March 31, 2021 and December 31, 2020, there were no collateral dependent available-for-sale or held-to-maturity securities.


	March 31, 2021
	Less than 12 Months					12 Months or Longer					Total
	Number	Fair Value		Gross Unrealized Losses		Number	Fair Value		Gross Unrealized Losses		Number	Fair Value		Gross Unrealized Losses
	(Dollars in thousands)
Investment securities available-for-sale:

Agency	28	$	389,387	$	(10,094)	9	$	9,947	$	(285)	37	$	399,334	$	(10,379)
Corporate	18	152,134		(4,911)		—	—		—		18	152,134		(4,911)
Municipal bonds	173	921,332		(32,394)		—	—		—		173	921,332		(32,394)
Collateralized mortgage obligations	32	309,975		(5,708)		1	388		(2)		33	310,363		(5,710)
Mortgage-backed securities.	70	671,400		(16,964)		—	—		—		70	671,400		(16,964)
Total investment securities available-for-sale	321	$	2,444,228	$	(70,071)	10	$	10,335	$	(287)	331	$	2,454,563	$	(70,358)


	December 31, 2020
	Less than 12 Months					12 Months or Longer					Total
	Number	Fair Value		Gross Unrealized Losses		Number	Fair Value		Gross Unrealized Losses		Number	Fair Value		Gross Unrealized Losses
	(Dollars in thousands)
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)


	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
	Amortized Cost		Fair Value		Amortized Cost		Fair Value		Amortized Cost		Fair Value		Amortized Cost		Fair Value		Amortized Cost		Fair Value
	(Dollars in thousands)
Investment securities available-for-sale:
U.S. Treasury	$	—	$	—	$	30,144	$	32,063	$	—	$	—	$	—	$	—	$	30,144	$	32,063
Agency	—		—		322,038		325,584		251,286		252,084		87,258		85,491		660,582		663,159
Corporate	94,711		94,917		9,683		9,645		218,847		218,536		37,376		34,736		360,617		357,834
Municipal bonds	11,286		11,286		4,622		4,912		36,182		38,652		1,380,079		1,367,212		1,432,169		1,422,062
Collateralized mortgage obligations	—		—		27,394		27,373		211,472		207,662		275,384		273,936		514,250		508,971
Mortgage-backed securities	—		—		2,144		2,283		190,923		195,067		687,836		675,898		880,903		873,248
Total investment securities available-for-sale	105,997		106,203		396,025		401,860		908,710		912,001		2,467,933		2,437,273		3,878,665		3,857,337
Investment securities held-to-maturity:
Mortgage-backed securities	—		—		—		—		—		—		20,353		21,426		20,353		21,426
Other	—		—		—		—		—		—		1,578		1,578		1,578		1,578
Total investment securities held-to-maturity	—		—		—		—		—		—		21,931		23,004		21,931		23,004
Total investment securities	$	105,997	$	106,203	$	396,025	$	401,860	$	908,710	$	912,001	$	2,489,864	$	2,460,277	$	3,900,596	$	3,880,341

During the three months ended March 31, 2021, December 31, 2020, and March 31, 2020, the Company recognized gross gains on sales of available-for-sale securities in the amount of $4.2 million, $5.3 million, and $8.0 million, respectively. During the three months ended March 31, 2021, December 31, 2020, and March 31, 2020, the Company recognized gross losses on sales of available-for-sale securities in the amount of $191,000, $285,000, and $204,000, respectively. The Company had net proceeds from the sales of available-for-sale securities of $179.4 million, $207.6 million, and $97.9 million, during the three months ended March 31, 2021, December 31, 2020, and March 31, 2020, respectively.

The Company’s equity securities primarily consist of FHLB and Federal Reserve Bank of San Francisco (“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 March 31, 2021, the Company had $17.3 million in FHLB stock, $74.5 million in FRB stock and $26.1 million in other stock, all carried at cost. During the three months ended March 31, 2021, December 31, 2020, and March 31, 2020, the FHLB did not repurchase any of the Company’s excess FHLB stock through its stock repurchase program.

The Company accounts for credit losses on debt securities in accordance with ASC 326, which requires the Company to record an ACL on held-to-maturity investment securities at the time of purchase or acquisition. The ACL for held-to-maturity investment securities represents the Company’s current estimate of expected credit losses that may be incurred over the life of the investment. 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 to be credit related through the Company’s qualitative assessment. Non-credit related declines in fair value of available-for-sale investment securities are not recorded through an ACL, but rather recorded as an adjustment to accumulated other comprehensive income, net of tax. 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.

The Company did not record an ACL for available-for-sale or held-to-maturity investment securities during the three months ended March 31, 2021, December 31, 2020, and March 31, 2020. For available-for-sale securities where estimated fair value was below amortized cost, such declines were deemed non-credit related and recorded as an adjustment to accumulated other comprehensive income, net of tax. Non-credit related decline in fair value of available-for-sale investment securities can be attributed to changes in interest rates and other market related factors. The Company did not record an ACL for held-to maturity securities during the three months ended March 31, 2021, December 31, 2020, and March 31, 2020 because the likelihood of non-repayment is remote.


	Vintage
	2021		2020		2019		2018		2017		Prior		Total
	(Dollars in thousands)
Investment securities available-for-sale:
U.S. Treasury
Aaa - Aa3	$	—	$	—	$	—	$	21,510	$	10,553	$	—	$	32,063


Agency
Aaa - Aa3	—		352,414		73,090		151,364		9,075		77,216		663,159


Corporate debt

A1 - A3	—		56,760		—		—		—		93,295		150,055
Baa1 - Baa3	—		98,707		69,231		—		17,919		21,922		207,779
Municipal bonds
Aaa - Aa3	11,286		994,512		285,174		32,304		59,458		35,689		1,418,423
A1 - A3	—		—		—		—		—		2,313		2,313
Baa1 - Baa3	—		—		—		—		—		1,326		1,326
Collateralized mortgage obligations
Aaa - Aa3	17,334		241,843		93,697		25,311		14,634		116,152		508,971


Mortgage-backed securities
Aaa - Aa3	185,205		458,327		109,257		13,155		47,529		59,775		873,248


Total investment securities available-for-sale	213,825		2,202,563		630,449		243,644		159,168		407,688		3,857,337
Investment securities held-to-maturity:
Mortgage-backed securities
Aaa - Aa3	—		—		—		5,822		5,186		9,345		20,353


Other


Baa1 - Baa3	—		—		—		617		—		961		1,578
Total investment securities held-to-maturity	—		—		—		6,439		5,186		10,306		21,931
Total investment securities	$	213,825	$	2,202,563	$	630,449	$	250,083	$	164,354	$	417,994	$	3,879,268