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, investments in qualified affordable housing projects, as well as public equity securities held as a result of equity warrant assets exercised.


	September 30, 2020
(Dollars in thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses		Carrying Value
Available-for-sale securities, at fair value:
U.S. Treasury securities	$	4,251,342	$	295,952	$	—	$	4,547,294
U.S. agency debentures	150,000		2,526		—		152,526
Foreign government debt securities	23,452		—		(3)		23,449
Residential mortgage-backed securities:
Agency-issued mortgage-backed securities	9,569,724		200,691		(102)		9,770,313
Agency-issued collateralized mortgage obligations—fixed rate	7,277,652		45,809		(7,488)		7,315,973

Agency-issued commercial mortgage-backed securities	3,965,370		130,384		(985)		4,094,769

Total available-for-sale securities	$	25,237,540	$	675,362	$	(8,578)	$	25,904,324


	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

The following table summarizes sale activity of available-for-sale securities during the three and nine months ended September 30, 2020 and 2019 as recorded in the line item “Gains on investment securities, net," a component of noninterest income:


	Three months ended September 30,				Nine months ended September 30,
(Dollars in thousands)	2020		2019		2020		2019
Sales proceeds	$	—	$	—	$	2,654,212	$	2,189,087
Net realized gains and losses:
Gross realized gains	—		—		61,165		1,250
Gross realized losses	—		—		—		(5,155)
Net realized gains (losses)	$	—	$	—	$	61,165	$	(3,905)

The following tables summarize our available-for-sale 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 September 30, 2020 and December 31, 2019:


	September 30, 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:


Foreign government debt securities	$	23,449	$	(3)	$	—	$	—	$	23,449	$	(3)
Residential mortgage-backed securities:
Agency-issued mortgage-backed securities	179,050		(102)		—		—		179,050		(102)
Agency-issued collateralized mortgage obligations—fixed rate	1,772,593		(7,488)		—		—		1,772,593		(7,488)

Agency-issued commercial mortgage-backed securities	518,223		(985)		—		—		518,223		(985)
Total available-for-sale securities (1)	$	2,493,315	$	(8,578)	$	—	$	—	$	2,493,315	$	(8,578)

(1)As of September 30, 2020, we identified a total of 57 investments that were in unrealized loss positions with no investment in an unrealized loss position for a period of time greater than 12 months. Based on our analysis of the securities in an unrealized loss position as of September 30, 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 available-for-sale securities portfolio are reviewed and monitored on a quarterly basis. As of September 30, 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 available-for-sale securities portfolio were past due as of September 30, 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 available-for-sale as of September 30, 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 available-for-sale 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.


	September 30, 2020
(Dollars in thousands)	Total		One Year or Less		After One Year to Five Years		After Five Years to Ten Years		After Ten Years
U.S. Treasury securities	$	4,547,294	$	60,221	$	2,989,181	$	1,497,892	$	—
U.S. agency debentures	152,526		—		—		152,526		—
Foreign government debt securities	23,449		23,449		—		—		—
Residential mortgage-backed securities:
Agency-issued mortgage-backed securities	9,770,313		—		—		—		9,770,313
Agency-issued collateralized mortgage obligations—fixed rate	7,315,973		—		—		—		7,315,973

Agency-issued commercial mortgage-backed securities	4,094,769		—		—		1,431,547		2,663,222
Total	$	25,904,324	$	83,670	$	2,989,181	$	3,081,965	$	19,749,508


	September 30, 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)	$	402,346	$	19,496	$	—	$	421,842	$	—
Residential mortgage-backed securities:
Agency-issued mortgage-backed securities	5,363,541		266,455		(62)		5,629,934		—
Agency-issued collateralized mortgage obligations —fixed rate	1,909,965		26,601		(437)		1,936,129		—
Agency-issued collateralized mortgage obligations—variable rate	147,714		362		—		148,076		—
Agency-issued commercial mortgage-backed securities	2,229,811		154,061		—		2,383,872		—
Municipal bonds and notes	2,929,137		171,591		(8,118)		3,092,610		291
Total held-to-maturity securities	$	12,982,514	$	638,566	$	(8,617)	$	13,612,463	$	291


	December 31, 2019
(Dollars in thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
Held-to-maturity securities, at amortized 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


Three months ended September 30,	Beginning Balance June 30, 2020		Provision for Credit Losses		Ending Balance September 30, 2020
(Dollars in thousands)
Municipal bonds and notes	$	222	$	69	$	291
Total allowance for credit losses	$	222	$	69	$	291


Nine months ended September 30,	Beginning Balance December 31, 2019		Day One Impact of adopting ASC 326		Provision for Credit Losses		Ending Balance September 30, 2020
(Dollars in thousands)
Municipal bonds and notes	$	—	$	174	$	117	$	291
Total allowance for credit losses	$	—	$	174	$	117	$	291

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 September 30, 2020:

The following table summarizes the remaining contractual principal maturities on fixed income investment securities classified as held-to-maturity as of September 30, 2020. For U.S. agency debentures, the expected maturity is the actual contractual maturity of the notes. Expected remaining maturities for certain U.S. agency debentures may occur earlier than their contractual maturities because the note issuers have the right to call outstanding amounts ahead of their contractual maturity. 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 held-to-maturity 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.


	September 30, 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	$	402,346	$	421,842	$	4,675	$	4,720	$	148,559	$	153,787	$	249,112	$	263,335	$	—	$	—
Residential mortgage-backed securities:
Agency-issued mortgage-backed securities	5,363,541		5,629,934		7,113		7,432		28,722		29,739		588,606		609,151		4,739,100		4,983,612
Agency-issued collateralized mortgage obligations—fixed rate	1,909,965		1,936,129		—		—		—		—		551,213		563,127		1,358,752		1,373,002
Agency-issued collateralized mortgage obligations—variable rate	147,714		148,076		—		—		—		—		—		—		147,714		148,076
Agency-issued commercial mortgage-backed securities	2,229,811		2,383,872		—		—		—		—		102,428		120,085		2,127,383		2,263,787
Municipal bonds and notes	2,929,137		3,092,610		44,340		44,839		134,029		140,191		540,308		587,096		2,210,460		2,320,484
Total	$	12,982,514	$	13,612,463	$	56,128	$	56,991	$	311,310	$	323,717	$	2,031,667	$	2,142,794	$	10,583,409	$	11,088,961


(Dollars in thousands)	September 30, 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)	$	74,293	$	87,180
Unconsolidated venture capital and private equity fund investments (2)	152,367		178,217
Other investments without a readily determinable fair value (3)	56,008		55,255
Other equity securities in public companies (fair value accounting) (4)	229,297		59,200
Non-marketable securities (equity method accounting) (5):
Venture capital and private equity fund investments	274,721		215,367
Debt funds	6,918		7,271
Other investments	192,776		152,863
Investments in qualified affordable housing projects, net (6)	560,983		458,476
Total non-marketable and other equity securities	$	1,547,363	$	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 September 30, 2020 and December 31, 2019 (fair value accounting):


	September 30, 2020				December 31, 2019
(Dollars in thousands)	Amount		Ownership %		Amount		Ownership %
Strategic Investors Fund, LP	$	4,646	12.6	%	$	5,729	12.6	%
Capital Preferred Return Fund, LP	39,246		20.0		45,341		20.0
Growth Partners, LP	30,267		33.0		35,976		33.0
CP I, LP	134		10.7		134		10.7
Total consolidated venture capital and private equity fund investments	$	74,293			$	87,180

(2)The carrying value represents investments in 179 and 205 funds (primarily venture capital funds) at September 30, 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 June 30th for our September 30th 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.


(Dollars in thousands)	Nine months ended September 30, 2020		Cumulative Adjustments
Measurement alternative:
Carrying value at September 30, 2020	$	56,008
Carrying value adjustments:
Impairment	$	(487)	$	(947)
Upward changes for observable prices	1,438		2,236
Downward changes for observable prices	(6,210)		(8,918)

(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 and direct equity investments in public companies held by our consolidated funds. Changes in equity securities measured at fair value are recognized through net income. This amount includes total unrealized gains of $108.4 million in BigCommerce Holdings, Inc. ("BigCommerce") which is currently subject to a lock-up agreement.


	September 30, 2020				December 31, 2019
(Dollars in thousands)	Amount		Ownership %		Amount		Ownership %
Venture capital and private equity fund investments:
Strategic Investors Fund II, LP	$	3,519	8.6	%	$	3,612	8.6	%
Strategic Investors Fund III, LP	14,984		5.9		15,668		5.9
Strategic Investors Fund IV, LP	25,451		5.0		27,064		5.0
Strategic Investors Fund V funds	52,575		Various		46,830		Various
CP II, LP (i)	4,773		5.1		5,907		5.1
Other venture capital and private equity fund investments	173,419		Various		116,286		Various
Total venture capital and private equity fund investments	$	274,721			$	215,367
Debt funds:
Gold Hill Capital 2008, LP (ii)	$	5,317	15.5	%	$	5,525	15.5	%
Other debt funds	1,601		Various		1,746		Various
Total debt funds	$	6,918			$	7,271
Other investments:
SPD Silicon Valley Bank Co., Ltd.	$	107,969	50.0	%	$	74,190	50.0	%
Other investments	84,807		Various		78,673		Various
Total other investments	$	192,776			$	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 September 30, 2020 and December 31, 2019:


	Three months ended September 30,				Nine months ended September 30,
(Dollars in thousands)	2020		2019		2020		2019
Tax credits and other tax benefits recognized	$	15,290	$	8,705	$	46,772	$	28,950
Amortization expense included in provision for income taxes (i)	10,222		6,042		32,081		20,436

The following table presents the net gains and losses on non-marketable and other equity securities for the three and nine months ended September 30, 2020 and 2019 as recorded in the line item “Gains on investment securities, net," a component of noninterest income:


	Three months ended September 30,				Nine months ended September 30,
(Dollars in thousands)	2020		2019		2020		2019
Net gains (losses) on non-marketable and other equity securities:
Non-marketable securities (fair value accounting):
Consolidated venture capital and private equity fund investments	$	8,778	$	4,555	$	13,168	$	22,674
Unconsolidated venture capital and private equity fund investments	16,400		8,530		15,187		26,688
Other investments without a readily determinable fair value	217		(471)		(3,619)		4,701
Other equity securities in public companies (fair value accounting)	112,615		(11,979)		118,099		106
Non-marketable securities (equity method accounting):
Venture capital and private equity fund investments	51,334		29,049		69,681		54,189
Debt funds	15		187		(253)		1,529
Other investments	478		(22)		(2,668)		593
Total net gains on non-marketable and other equity securities	$	189,837	$	29,849	$	209,595	$	110,480






Less: realized net gains on sales of non-marketable and other equity securities	5,262		277		5,477		12,637
Net gains on non-marketable and other equity securities still held	$	184,575	$	29,572	$	204,118	$	97,843