
	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 obligation	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


	December 31, 2019
	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss		Estimated Fair Value
	(Dollars in thousands)
Investment securities available-for-sale:
U.S. Treasury	$	60,457	$	3,137	$	(39)	$	63,555
Agency	240,348		7,686		(1,676)		246,358
Corporate	149,150		2,217		(14)		151,353
Municipal bonds	384,032		13,450		(184)		397,298
Collateralized mortgage obligation	9,869		123		(8)		9,984
Mortgage-backed securities	494,404		7,603		(2,171)		499,836
Total investment securities available-for-sale	1,338,260		34,216		(4,092)		1,368,384
Investment securities held-to-maturity:
Mortgage-backed securities	36,114		922		—		37,036
Other	1,724		—		—		1,724
Total investment securities held-to-maturity	37,838		922		—		38,760
Total investment securities	$	1,376,098	$	35,138	$	(4,092)	$	1,407,144

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, 2020, the Company had accumulated other comprehensive income of $84.4 million, or $60.3 million net of tax, compared to accumulated other comprehensive income of $30.1 million, or $21.5 million net of tax, at December 31, 2019.

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 December 31, 2020 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, 2020, 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, 2020. There were no other than temporary impairment losses recognized for investment securities for the years ended December 31, 2019 and 2018.

At 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 December 31, 2020 and December 31, 2019, there were no securities purchased with deterioration in credit quality since their origination. At December 31, 2019, there were no collateral dependent available-for-sale or held-to-maturity securities.


	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 obligation	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)


	December 31, 2019
	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:
U.S. Treasury	1	$	10,194	$	(39)	—	$	—	$	—	1	$	10,194	$	(39)
Agency	13	102,874		(1,340)		9	13,514		(336)		22	116,388		(1,676)
Corporate	1	1,017		(14)		—	—		—		1	1,017		(14)
Municipal bonds	12	30,541		(184)		—	—		—		12	30,541		(184)
Collateralized mortgage obligation	—	—		—		1	603		(8)		1	603		(8)
Mortgage-backed securities	18	130,014		(1,681)		11	26,886		(490)		29	156,900		(2,171)
Total investment securities available-for-sale	45	$	274,640	$	(3,258)	21	$	41,003	$	(834)	66	$	315,643	$	(4,092)


	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:
Treasury	$	—	$	—	$	30,153	$	32,533	$	—	$	—	$	—	$	—	$	30,153	$	32,533
Agency	—		—		357,471		365,530		216,904		227,338		92,327		97,518		666,702		690,386
Corporate	146,122		146,471		9,696		9,714		218,964		221,753		37,441		37,370		412,223		415,308
Municipal bonds	9,922		10,525		3,456		3,743		34,623		37,721		1,364,011		1,394,030		1,412,012		1,446,019
Collateralized mortgage obligation	—		—		14,938		14,869		219,553		219,509		278,768		278,988		513,259		513,366
Mortgage-backed securities	—		—		2,167		2,313		204,924		216,932		605,293		614,258		812,384		833,503
Total investment securities available-for-sale	156,044		156,996		417,881		428,702		894,968		923,253		2,377,840		2,422,164		3,846,733		3,931,115
Investment securities held-to-maturity:
Mortgage-backed securities	—		—		—		—		—		—		22,124		23,405		22,124		23,405
Other	—		—		—		—		—		—		1,608		1,608		1,608		1,608
Total investment securities held-to-maturity	—		—		—		—		—		—		23,732		25,013		23,732		25,013
Total investment securities	$	156,044	$	156,996	$	417,881	$	428,702	$	894,968	$	923,253	$	2,401,572	$	2,447,177	$	3,870,465	$	3,956,128

During the years ended December 31, 2020, 2019, and 2018, the Company recognized gross realized gains on sales of available-for-sale securities in the amounts of $15.7 million, $10.3 million, and $1.6 million, respectively. During the years ended December 31, 2020, 2019, and 2018, the Company recognized gross realized losses on sales of available-for-sale securities in the amounts of $1.8 million, $1.8 million, and $208,000, respectively. The Company had net proceeds from the sale of available-for-sale securities of $766.5 million, $551.8 million, and $407.0 million during the years ended December 31, 2020, 2019, and 2018, respectively.

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 Federal Reserve System. These equity securities without readily determinable fair values are carried at cost less impairment. At December 31, 2020, the Company had $17.3 million in FHLB stock, $74.4 million in Federal Reserve Bank of San Francisco (“FRB”) stock, and $25.4 million in other stock, all carried at cost. During the years ended December 31, 2020, 2019, and 2018, FHLB had repurchased $17.3 million, $18.3 million, and $24.9 million, respectively, of the Company’s excess FHLB stock through their stock repurchase program. The Company evaluates its investments in FHLB and other stock for impairment periodically, including their capital adequacy and overall financial condition. No impairment losses have been recorded through December 31, 2020.

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 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 year ended December 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 year ended December 31, 2020, because the likelihood of non-repayment is remote.


	December 31, 2020
	Vintage
	2020		2019		2018		2017		2016		Prior		Total
	(Dollars in thousands)
Investment securities available-for-sale:
U.S. Treasury
Aaa - Aa3	$	—	$	—	$	21,852	$	10,681	$	—	$	—	$	32,533


Agency
Aaa - Aa3	359,428		60,943		157,942		9,733		20,711		81,629		690,386


Corporate debt

A1 - A3	60,858		—		—		—		118,631		9,145		188,634
Baa1 - Baa3	99,999		69,638		5,034		17,936		5,449		28,618		226,674
Municipal bonds
Aaa - Aa3	1,022,544		290,007		32,798		60,595		15,294		23,919		1,445,157
A1 - A3	—		—		—		—		—		862		862

Collateralized mortgage obligations
Aaa - Aa3	241,971		107,104		29,890		15,305		105,641		13,455		513,366


Mortgage-backed securities
Aaa - Aa3	424,825		112,447		32,901		144,513		39,975		78,842		833,503


Total investment securities available-for-sale	2,209,625		640,139		280,417		258,763		305,701		236,470		3,931,115
Investment securities held-to-maturity:
Mortgage-backed securities
Aaa - Aa3	—		—		6,552		5,372		4,209		5,991		22,124


Other


Baa1 - Baa3	—		—		633		—		—		975		1,608
Total investment securities held-to-maturity	—		—		7,185		5,372		4,209		6,966		23,732
Total investment securities	$	2,209,625	$	640,139	$	287,602	$	264,135	$	309,910	$	243,436	$	3,954,847