Our investment securities portfolio consists of (i) an available-for-sale securities portfolio and a held-to-maturity securities portfolio, both of which represent interest-earning investment securities; and (ii) a non-marketable and other equity securities portfolio, which primarily represents investments managed as part of our funds management business as well as public equity securities held as a result of equity warrant assets exercised.


	December 31, 2020
(Dollars in thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses		Carrying Value
Available-for-sale securities, at fair value:
U.S. Treasury securities	$	4,197,858	$	271,977	$	(107)	$	4,469,728
U.S. agency debentures	233,727		4,165		(585)		237,307
Foreign government debt securities	24,491		1		—		24,492
Residential mortgage-backed securities:
Agency-issued mortgage-backed securities	13,271,482		232,850		(651)		13,503,681
Agency-issued collateralized mortgage obligations—fixed rate	8,076,832		40,010		(10,278)		8,106,564
Agency-issued commercial mortgage-backed securities	4,440,506		133,527		(3,367)		4,570,666
Total available-for-sale securities	$	30,244,896	$	682,530	$	(14,988)	$	30,912,438


	December 31, 2019
(Dollars in thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses		Carrying Value
Available-for-sale securities, at fair value:
U.S. Treasury securities	$	6,815,874	$	82,267	$	(4,131)	$	6,894,010
U.S. agency debentures	100,000		—		(453)		99,547
Foreign government debt securities	9,037		1		—		9,038
Residential mortgage-backed securities:
Agency-issued mortgage-backed securities	4,109,372		39,438		(19)		4,148,791
Agency-issued collateralized mortgage obligations—fixed rate	1,520,414		17,929		—		1,538,343
Agency-issued commercial mortgage-backed securities	1,339,651		1,078		(15,539)		1,325,190

Total available-for-sale securities	$	13,894,348	$	140,713	$	(20,142)	$	14,014,919


	Year ended December 31,
(Dollars in thousands)	2020		2019		2018
Sales proceeds	$	2,654,212	$	2,189,087	$	474,482
Net realized gains and losses:
Gross realized gains	61,165		1,250		127
Gross realized losses	—		(5,155)		(867)
Net realized losses	$	61,165	$	(3,905)	$	(740)

The following tables summarize our AFS securities in an unrealized loss position for which an allowance for credit losses has not been recorded and summarized into categories of less than 12 months, or 12 months or longer as of December 31, 2020 and 2019:


	December 31, 2020
	Less than 12 months				12 months or longer (1)				Total
(Dollars in thousands)	Fair Value of Investments		Unrealized Losses		Fair Value of Investments		Unrealized Losses		Fair Value of Investments		Unrealized Losses
Available-for-sale securities:
U.S. Treasury securities	$	59,929	$	(107)	$	—	$	—	$	59,929	$	(107)
U.S. agency debentures	133,143		(585)		—		—		133,143		(585)

Residential mortgage-backed securities:
Agency-issued mortgage-backed securities	903,767		(651)		—		—		903,767		(651)
Agency-issued collateralized mortgage obligations—fixed rate	2,199,207		(10,278)		—		—		2,199,207		(10,278)
Agency-issued commercial mortgage-backed securities	989,389		(3,367)		—		—		989,389		(3,367)
Total available-for-sale securities (1)	$	4,285,435	$	(14,988)	$	—	$	—	$	4,285,435	$	(14,988)

(1)As of December 31, 2020, we identified a total of 93 investments that were in unrealized loss positions with no investments in unrealized loss positions for a period of time greater than 12 months. Based on our analysis of the securities in an unrealized loss position as of December 31, 2020, the decline in value is unrelated to credit loss and is related to changes in market interest rates since purchase and therefore changes in value for securities are included in other comprehensive income. Market valuations and credit loss analyses on assets in the AFS securities portfolio are reviewed and monitored on a quarterly basis. As of December 31, 2020, we do not intend to sell any of our securities in an unrealized loss position prior to recovery of our amortized cost basis, and it is more likely than not that we will not be required to sell any of our securities prior to recovery of our amortized cost basis. None of the investments in our AFS securities portfolio were past due as of December 31, 2020.


	December 31, 2019
	Less than 12 months				12 months or longer (1)				Total
(Dollars in thousands)	Fair Value of Investments		Unrealized Losses		Fair Value of Investments		Unrealized Losses		Fair Value of Investments		Unrealized Losses
Available-for-sale securities:
U.S. Treasury securities	$	971,572	$	(3,996)	$	449,850	$	(135)	$	1,421,422	$	(4,131)
U.S. agency debentures	99,547		(453)		—		—		99,547		(453)

Residential mortgage-backed securities:
Agency-issued mortgage-backed securities	4,014		(19)		—		—		4,014		(19)
Agency-issued commercial mortgage-backed securities	1,027,232		(15,539)		—		—		1,027,232		(15,539)

Total available-for-sale securities (1)	$	2,102,365	$	(20,007)	$	449,850	$	(135)	$	2,552,215	$	(20,142)

(1)As of December 31, 2019, we identified a total of 58 investments that were in unrealized loss positions, of which 12 investments totaling $0.4 billion with unrealized losses of $0.1 million have been in an unrealized loss position for a period of time greater than 12 months.

The following table summarizes the fixed income securities, carried at fair value, classified as AFS as of December 31, 2020 by the remaining contractual principal maturities. For U.S. Treasury securities, U.S. agency debentures and foreign government debt securities, the expected maturity is the actual contractual maturity of the notes. Expected maturities for mortgage-backed securities may differ significantly from their contractual maturities because mortgage borrowers have the right to prepay outstanding loan obligations with or without penalties. Mortgage-backed securities classified as AFS typically have original contractual maturities from 10 to 30 years whereas expected average lives of these securities tend to be significantly shorter and vary based upon structure and prepayments in lower interest rate environments.


	December 31, 2020
(Dollars in thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value		Allowance for Credit Losses (2)
Held-to-maturity securities, at cost:
U.S. agency debentures (1)	$	402,265	$	18,961	$	—	$	421,226	$	—
Residential mortgage-backed securities:
Agency-issued mortgage-backed securities	7,739,763		240,121		(2,211)		7,977,673		—
Agency-issued collateralized mortgage obligations—fixed rate	1,735,451		23,227		(296)		1,758,382		—
Agency-issued collateralized mortgage obligations—variable rate	136,913		317		—		137,230		—
Agency-issued commercial mortgage-backed securities	2,942,959		123,846		—		3,066,805		—
Municipal bonds and notes	3,635,194		220,866		(505)		3,855,555		392
Total held-to-maturity securities	$	16,592,545	$	627,338	$	(3,012)	$	17,216,871	$	392


	December 31, 2019
(Dollars in thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
Held-to-maturity securities, at cost:
U.S. agency debentures (1)	$	518,728	$	6,640	$	(668)	$	524,700
Residential mortgage-backed securities:
Agency-issued mortgage-backed securities	6,992,009		142,209		(2,066)		7,132,152
Agency-issued collateralized mortgage obligations—fixed rate	1,608,032		592		(8,502)		1,600,122
Agency-issued collateralized mortgage obligations—variable rate	178,611		94		(259)		178,446
Agency-issued commercial mortgage-backed securities	2,759,615		56,914		(4,508)		2,812,021
Municipal bonds and notes	1,785,951		83,314		(1,434)		1,867,831
Total held-to-maturity securities	$	13,842,946	$	289,763	$	(17,437)	$	14,115,272


Year ended December 31, 2020:	Beginning Balance December 31, 2019		Day One Impact of Adopting ASC 326		Provision for HTM Securities		Ending Balance December 31, 2020
(Dollars in thousands)
Municipal bonds and notes	$	—	$	174	$	218	$	392
Total allowance for credit losses	$	—	$	174	$	218	$	392

On a quarterly basis, management monitors the credit quality for HTM securities through the use of standard credit ratings. The following table summarizes our amortized cost of HTM securities aggregated by credit quality indicator at December 31, 2020:

The following table summarizes the remaining contractual principal maturities on fixed income investment securities classified as HTM as of December 31, 2020. For U.S. agency debentures, the expected maturity is the actual contractual maturity of the notes. Expected maturities for mortgage-backed securities may differ significantly from their contractual maturities because mortgage borrowers have the right to prepay outstanding loan obligations with or without penalties. Mortgage-backed securities classified as HTM typically have original contractual maturities from 10 to 30 years whereas expected average lives of these securities tend to be significantly shorter and vary based upon structure and prepayments in lower interest rate environments.


	December 31, 2020
	Total				One Year or Less				After One Year to Five Years				After Five Years to Ten Years				After Ten Years
(Dollars in thousands)	Amortized Cost		Fair Value		Amortized Cost		Fair Value		Amortized Cost		Fair Value		Amortized Cost		Fair Value		Amortized Cost		Fair Value
U.S. agency debentures	$	402,265	$	421,226	$	4,675	$	4,705	$	148,478	$	153,756	$	249,112	$	262,765	$	—	$	—
Residential mortgage-backed securities:
Agency-issued mortgage-backed securities	7,739,763		7,977,673		4,762		4,951		20,389		21,150		540,731		559,727		7,173,881		7,391,845
Agency-issued collateralized mortgage obligations - fixed rate	1,735,451		1,758,382		—		—		5,952		6,073		494,532		505,156		1,234,967		1,247,153
Agency-issued collateralized mortgage obligations - variable rate	136,913		137,230		—		—		—		—		—		—		136,913		137,230
Agency-issued commercial mortgage-backed securities	2,942,959		3,066,805		—		—		—		—		102,359		119,922		2,840,600		2,946,883
Municipal bonds and notes	3,635,194		3,855,555		46,292		46,641		144,347		150,940		669,281		721,554		2,775,274		2,936,420
Total	$	16,592,545	$	17,216,871	$	55,729	$	56,297	$	319,166	$	331,919	$	2,056,015	$	2,169,124	$	14,161,635	$	14,659,531


(Dollars in thousands)	December 31, 2020		December 31, 2019
Non-marketable and other equity securities:
Non-marketable securities (fair value accounting):
Consolidated venture capital and private equity fund investments (1)	$	88,937	$	87,180
Unconsolidated venture capital and private equity fund investments (2)	184,886		178,217
Other investments without a readily determinable fair value (3)	60,975		55,255
Other equity securities in public companies (fair value accounting) (4)	280,804		59,200
Non-marketable securities (equity method accounting) (5):
Venture capital and private equity fund investments	362,192		215,367
Debt funds	5,444		7,271
Other investments	202,809		152,863
Investments in qualified affordable housing projects, net (6)	616,188		458,476
Total non-marketable and other equity securities	$	1,802,235	$	1,213,829

(1)The following table shows the amounts of venture capital and private equity fund investments held by the following consolidated funds and our ownership percentage of each fund at December 31, 2020 and 2019 (fair value accounting):


	December 31, 2020				December 31, 2019
(Dollars in thousands)	Amount		Ownership %		Amount		Ownership %
Strategic Investors Fund, LP	$	4,850	12.6	%	$	5,729	12.6	%
Capital Preferred Return Fund, LP	49,574		20.0		45,341		20.0
Growth Partners, LP	34,513		33.0		35,976		33.0
CP I, LP	—		—		134		10.7
Total consolidated venture capital and private equity fund investments	$	88,937			$	87,180

(2)The carrying value represents investments in 162 and 205 funds (primarily venture capital funds) at December 31, 2020 and December 31, 2019, respectively, where our ownership interest is typically less than 5% of the voting interests of each such fund and in which we do not have the ability to exercise significant influence over the partnerships operating activities and financial policies. We carry our unconsolidated venture capital and private equity fund investments at fair value based on the fund investments' net asset values per share as obtained from the general partners of the investments. For each fund investment, we adjust the net asset value per share for differences between our measurement date and the date of the fund investment’s net asset value by using the most recently available financial information from the investee general partner, for example September 30th for our December 31st consolidated financial statements, adjusted for any contributions paid, distributions received from the investment, and significant fund transactions or market events during the reporting period.

(3)These investments include direct equity investments in private companies. The carrying value is based on the price at which the investment was acquired plus or minus changes resulting from observable price changes in orderly transactions for identical or similar investments. We consider a range of factors when adjusting the fair value of these investments, including, but not limited to, the term and nature of the investment, local market conditions, values for comparable securities, current and projected operating performance, exit strategies, financing transactions subsequent to the acquisition of the investment and a discount for certain investments that have lock-up restrictions or other features that indicate a discount to fair value is warranted.

The following table shows the carrying amount of other investments without a readily determinable fair value at December 31, 2020, and the amounts recognized in earnings for the year ended December 31, 2020 and on a cumulative basis:


(Dollars in thousands)	Year ended December 31, 2020		Cumulative Adjustments
Measurement alternative:
Carrying value at December 31, 2020	$	60,975
Carrying value adjustments:
Impairment	$	(487)	$	(947)
Upward changes for observable prices	3,479		4,216
Downward changes for observable prices	(2,799)		(3,898)

(4)Investments classified as other equity securities (fair value accounting) represent shares held in public companies as a result of exercising public equity warrant assets, direct equity investments in public companies held by our consolidated funds, and exchange traded funds held by SVB Leerink. Changes in equity securities measured at fair value are recognized through net income.


	December 31, 2020				December 31, 2019
(Dollars in thousands)	Amount		Ownership %		Amount		Ownership %
Venture capital and private equity fund investments:
Strategic Investors Fund II, LP	$	3,705	8.6	%	$	3,612	8.6	%
Strategic Investors Fund III, LP	16,110		5.9		15,668		5.9
Strategic Investors Fund IV, LP	25,169		5.0		27,064		5.0
Strategic Investors Fund V funds	67,052		Various		46,830		Various
CP II, LP (i)	7,887		5.1		5,907		5.1
Other venture capital and private equity fund investments	242,269		Various		116,286		Various
Total venture capital and private equity fund investments	$	362,192			$	215,367
Debt funds:
Gold Hill Capital 2008, LP (ii)	$	3,941	15.5	%	$	5,525	15.5	%
Other debt funds	1,503		Various		1,746		Various
Total debt funds	$	5,444			$	7,271
Other investments:
SPD Silicon Valley Bank Co., Ltd.	$	115,232	50.0	%	$	74,190	50.0	%
Other investments	87,577		Various		78,673		Various
Total other investments	$	202,809			$	152,863

(6)The following table presents the balances of our investments in qualified affordable housing projects and related unfunded commitments included as a component of "other liabilities" on our consolidated balance sheets at December 31, 2020 and 2019:


	Year ended December 31,
(Dollars in thousands)	2020		2019		2018
Net gains (losses) on non-marketable and other equity securities:
Non-marketable securities (fair value accounting):
Consolidated venture capital and private equity fund investments	$	32,439	$	22,507	$	20,999
Unconsolidated venture capital and private equity fund investments	59,909		31,482		39,075
Other investments without a readily determinable fair value	253		2,742		3,206
Other equity securities in public companies (fair value accounting)	104,865		7,772		(25,483)
Non-marketable securities (equity method accounting):
Venture capital and private equity fund investments	161,828		73,813		49,341
Debt funds	(403)		1,647		541
Other investments	696		(1,388)		1,155
Total net gains on non-marketable and other equity securities	$	359,587	$	138,575	$	88,834



Less: realized net gains (losses) on sales of non-marketable and other equity securities	23,344		4,744		(26,097)
Net gains on non-marketable and other equity securities still held	$	336,243	$	133,831	$	114,931