
(In thousands)	September 30, 2020		December 31, 2019
Available for sale debt securities	$	11,539,061	$	8,571,626
Trading debt securities	25,805		28,161
Equity securities:
Readily determinable fair value	2,803		2,929
No readily determinable fair value	1,400		1,280
Other:
Federal Reserve Bank stock	34,070		33,770
Federal Home Loan Bank stock	10,000		10,000
Private equity investments	78,462		94,122
Total investment securities (1)	$	11,691,601	$	8,741,888

The Company has elected to measure equity securities with no readily determinable fair value at cost minus impairment, if any, plus or minus changes resulting from observable price changes for the identical or similar investment of the same issuer. This portfolio includes the Company's holdings of Visa Class B shares, which have a carrying value of zero, as there have not been observable price changes in orderly transactions for identical or similar investments of the same issuer. During the period, the Company did not record any impairment or other adjustments to the carrying amount of these equity securities without a readily determinable fair value.

Other investment securities include Federal Reserve Bank (FRB) stock, Federal Home Loan Bank (FHLB) stock, and investments in portfolio concerns held by the Company's private equity subsidiaries. FRB stock and FHLB stock are held for debt and regulatory purposes. Investment in FRB stock is based on the capital structure of the investing bank, and investment in FHLB stock is tied to the level of borrowings from the FHLB. These holdings are carried at cost. The private equity investments, in the absence of readily ascertainable market values, are carried at estimated fair value.

The majority of the Company’s investment portfolio is comprised of available for sale debt securities, which are carried at fair value with changes in fair value reported in accumulated other comprehensive income (AOCI). A summary of the available for sale debt securities by maturity groupings as of September 30, 2020 is shown below. The investment portfolio includes agency mortgage-backed securities, which are guaranteed by agencies such as the FHLMC, FNMA, and GNMA, in addition to non-agency mortgage-backed securities, which have no guarantee but are collateralized by commercial and residential mortgages. Also included are certain other asset-backed securities, which are primarily collateralized by credit cards,

automobiles, student loans, and commercial loans. These securities differ from traditional debt securities primarily in that they may have uncertain maturity dates and are priced based on estimated prepayment rates on the underlying collateral.


(In thousands)	Amortized Cost		Fair Value
U.S. government and federal agency obligations:
Within 1 year	$	59,367	$	59,706
After 1 but within 5 years	489,042		521,797
After 5 but within 10 years	225,159		253,555

Total U.S. government and federal agency obligations	773,568		835,058
Government-sponsored enterprise obligations:
Within 1 year	55,185		54,770


After 10 years	35,818		40,531
Total government-sponsored enterprise obligations	91,003		95,301
State and municipal obligations:
Within 1 year	68,787		69,179
After 1 but within 5 years	764,831		803,168
After 5 but within 10 years	597,276		624,525
After 10 years	464,375		472,272
Total state and municipal obligations	1,895,269		1,969,144
Mortgage and asset-backed securities:
Agency mortgage-backed securities	5,919,500		6,081,802
Non-agency mortgage-backed securities	324,266		332,970
Asset-backed securities	1,633,988		1,658,579
Total mortgage and asset-backed securities	7,877,754		8,073,351
Other debt securities:
Within 1 year	23,565		23,701
After 1 but within 5 years	252,180		264,096
After 5 but within 10 years	240,814		249,136
After 10 years	28,195		29,274
Total other debt securities	544,754		566,207
Total available for sale debt securities	$	11,182,348	$	11,539,061

Investments in U.S. government and federal agency obligations include U.S. Treasury inflation-protected securities, which totaled $429.8 million, at fair value, at September 30, 2020. Interest paid on these securities increases with inflation and decreases with deflation, as measured by the Consumer Price Index.

As described in Note 1, the Company adopted ASU 2016-13, Measurement of Credit Losses on Financial Instruments, on January 1, 2020. The adoption of ASU 2016-13 had no impact to the Company's available for sale securities reported in its consolidated financial statements at January 1, 2020. For the three and nine months ended September 30, 2020, the Company did not recognize a credit loss expense on any available for sale debt securities.

The Company’s impairment policy requires a review of all securities for which fair value is less than amortized cost. Special emphasis is placed on securities whose credit rating has fallen below Baa3 (Moody's) or BBB- (Standard & Poor's), whose fair values have fallen more than 20% below purchase price, or who have been identified based on management’s judgment. These securities are placed on a watch list and cash flow analyses are prepared on an individual security basis. Inputs to these models include factors such as cash flow projections, contractual payments required, delinquency rates, credit support from other tranches, prepayment speeds, collateral loss severity rates (including loan to values), and various other information related to the underlying collateral. Stress tests are performed at varying levels of delinquency rates, prepayment speeds and loss severities in order to gauge probable ranges of credit loss. At September 30, 2020, the fair value of securities on this watch list was $53.3 million compared to $51.6 million at December 31, 2019.

The Company's model for establishing its allowance for credit losses uses cash flows projected to be received over the estimated life of the securities, discounted to present value, and compared to the current amortized cost bases of the securities. As of September 30, 2020, the Company did not identify any securities for which a credit loss exists. Significant inputs to the cash flow models used at September 30, 2020 to quantify credit losses included the following:

The table below summarizes debt securities available for sale in an unrealized loss position for which an allowance for credit losses has not been recorded at September 30, 2020. Unrealized losses on these available for sale securities have not been recognized into income because the issuers' bonds are of investment grade quality (rated Baa3, BBB- or higher), their fair values have not fallen more than 20% below purchase price, and they have not been identified by management as a security needing a more detailed review. Additionally, management does not intend to sell the securities, and it is more likely than not that management will not be required to sell the securities prior to their anticipated recovery. The cash flow analyses prepared for securities included on the watch list discussed above did not identify any instances where the present value of expected cash flows were less than the amortized cost basis of the security.

The following table summarizes debt securities available for sale in an unrealized loss position for which an allowance for credit losses has not been recorded at September 30, 2020, aggregated by major security type and length of impairment period.


	Less than 12 months				12 months or longer				Total
(In thousands)	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
September 30, 2020

Government-sponsored enterprise obligations	$	14,489	$	503	$	—	$	—	$	14,489	$	503
State and municipal obligations	84,876		578		—		—		84,876		578
Mortgage and asset-backed securities:
Agency mortgage-backed securities	287,620		5,402		—		—		287,620		5,402
Non-agency mortgage-backed securities	68,513		234		1,069		45		69,582		279
Asset-backed securities	97,592		1,100		245,198		6,196		342,790		7,296
Total mortgage and asset-backed securities	453,725		6,736		246,267		6,241		699,992		12,977
Other debt securities	43,600		493		—		—		43,600		493
Total	$	596,690	$	8,310	$	246,267	$	6,241	$	842,957	$	14,551


	Less than 12 months				12 months or longer				Total
(In thousands)	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
December 31, 2019
U.S. government and federal agency obligations	$	31,787	$	21	$	25,405	$	21	$	57,192	$	42
Government-sponsored enterprise obligations	6,155		187		—		—		6,155		187
State and municipal obligations	6,700		31		1,554		1		8,254		32
Mortgage and asset-backed securities:
Agency mortgage-backed securities	652,352		5,306		147,653		867		800,005		6,173
Non-agency mortgage-backed securities	102,931		254		189,747		451		292,678		705
Asset-backed securities	330,876		3,610		152,461		2,108		483,337		5,718
Total mortgage and asset-backed securities	1,086,159		9,170		489,861		3,426		1,576,020		12,596
Other debt securities	5,496		4		997		3		6,493		7
Total	$	1,136,297	$	9,413	$	517,817	$	3,451	$	1,654,114	$	12,864

The entire available for sale debt portfolio included $843.0 million of securities that were in a loss position at September 30, 2020, compared to $1.7 billion at December 31, 2019. The total amount of unrealized loss on these securities was $14.6 million

at September 30, 2020, an increase of $1.7 million compared to the loss at December 31, 2019. Securities with significant unrealized losses are discussed in the "Allowance for credit losses on available for sale debt securities" section above.

For debt securities classified as available for sale, the following table shows the amortized cost, fair value, and allowance for credit losses of securities available for sale at September 30, 2020 and the corresponding amounts of gross unrealized gains and losses (pre-tax) in AOCI, by security type.


(In thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Allowance for Credit Losses		Fair Value
September 30, 2020
U.S. government and federal agency obligations	$	773,568	$	61,490	$	—	$	—	$	835,058
Government-sponsored enterprise obligations	91,003		4,801		(503)		—		95,301
State and municipal obligations	1,895,269		74,453		(578)		—		1,969,144
Mortgage and asset-backed securities:
Agency mortgage-backed securities	5,919,500		167,704		(5,402)		—		6,081,802
Non-agency mortgage-backed securities	324,266		8,983		(279)		—		332,970
Asset-backed securities	1,633,988		31,887		(7,296)		—		1,658,579
Total mortgage and asset-backed securities	7,877,754		208,574		(12,977)		—		8,073,351
Other debt securities	544,754		21,946		(493)		—		566,207
Total	$	11,182,348	$	371,264	$	(14,551)	$	—	$	11,539,061

For debt securities classified as available for sale, the following table shows the amortized cost and fair value of securities available-for-sale at December 31, 2019 and the corresponding amounts of gross unrealized gains and losses (pre-tax) in AOCI, by security type.


(In thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
December 31, 2019
U.S. government and federal agency obligations	$	827,861	$	23,957	$	(42)	$	851,776
Government-sponsored enterprise obligations	138,734		730		(187)		139,277
State and municipal obligations	1,225,532		42,427		(32)		1,267,927
Mortgage and asset-backed securities:
Agency mortgage-backed securities	3,893,247		50,890		(6,173)		3,937,964
Non-agency mortgage-backed securities	796,451		14,036		(705)		809,782
Asset-backed securities	1,228,151		11,056		(5,718)		1,233,489
Total mortgage and asset-backed securities	5,917,849		75,982		(12,596)		5,981,235
Other debt securities	325,555		5,863		(7)		331,411
Total	$	8,435,531	$	148,959	$	(12,864)	$	8,571,626


	For the Nine Months Ended September 30
(In thousands)	2020		2019
Proceeds from sales of securities:
Available for sale debt securities	$	574,374	$	368,939
Equity securities	2		3,459
Other	—		7,243
Total proceeds	$	574,376	$	379,641

Investment securities gains (losses), net:
Available for sale debt securities:

Gains realized on sales	$	16,965	$	2,287
Losses realized on sales	—		(1,559)
Other-than-temporary impairment recognized on debt securities	—		(133)
Equity securities:

Gains realized on sales	2		2,865

Fair value adjustments, net	(126)		318
Other:
Gains realized on sales	—		1,094

Fair value adjustments, net	(18,116)		(998)
Total investment securities gains (losses), net	$	(1,275)	$	3,874

Net gains and losses on investment securities for the nine months ended September 30, 2020 included net gains of $17.0 million realized on sales of available for sale debt securities as well as net losses in fair value of $126 thousand and $18.1 million on equity securities and private equity investments, respectively, due to fair value adjustments.

At September 30, 2020, securities totaling $4.5 billion in fair value were pledged to secure public fund deposits, securities sold under agreements to repurchase, trust funds, and borrowings at the FRB and FHLB. Securities pledged under agreements pursuant to which the collateral may be sold or re-pledged by the secured parties approximated $218.0 million, while the remaining securities were pledged under agreements pursuant to which the secured parties may not sell or re-pledge the collateral. Except for obligations of various government-sponsored enterprises such as FNMA, FHLB and FHLMC, no investment in a single issuer exceeded 10% of stockholders’ equity.