The amortized cost and fair value of investments in fixed maturities classified as available for sale were as follows:


	Amortized Cost		Allowance for Expected Credit Losses		Gross Unrealized				Fair Value
(at September 30, 2021, in millions)					Gains		Losses
U.S. Treasury securities and obligations of U.S. government and government agencies and authorities	$	3,908	$	—	$	27	$	20	$	3,915
Obligations of states, municipalities and political subdivisions:
Local general obligation	18,064		—		1,022		72		19,014
Revenue	10,785		—		660		36		11,409
State general obligation	1,170		—		66		3		1,233
Pre-refunded	3,885		—		218		—		4,103
Total obligations of states, municipalities and political subdivisions	33,904		—		1,966		111		35,759
Debt securities issued by foreign governments	1,037		—		12		5		1,044
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities	1,727		—		89		1		1,815
All other corporate bonds	33,026		2		1,598		129		34,493
Redeemable preferred stock	12		—		2		—		14
Total	$	73,614	$	2	$	3,694	$	266	$	77,040


	Amortized Cost		Allowance for Expected Credit Losses		Gross Unrealized				Fair Value
(at December 31, 2020, in millions)					Gains		Losses
U.S. Treasury securities and obligations of U.S. government and government agencies and authorities	$	2,111	$	—	$	38	$	—	$	2,149
Obligations of states, municipalities and political subdivisions:
Local general obligation	17,289		—		1,370		2		18,657
Revenue	11,806		—		909		—		12,715
State general obligation	1,343		—		101		—		1,444
Pre-refunded	3,325		—		219		—		3,544
Total obligations of states, municipalities and political subdivisions	33,763		—		2,599		2		36,360
Debt securities issued by foreign governments	1,028		—		26		—		1,054
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities	2,222		—		139		—		2,361
All other corporate bonds	29,683		2		2,382		9		32,054
Redeemable preferred stock	23		—		2		—		25
Total	$	68,830	$	2	$	5,186	$	11	$	74,003

Pre-refunded bonds of $4.10 billion and $3.54 billion at September 30, 2021 and December 31, 2020, respectively, were bonds for which states or municipalities have established irrevocable trusts, almost exclusively comprised of U.S. Treasury securities and obligations of U.S. government and government agencies and authorities. These trusts were created to fund the payment of principal and interest due under the bonds.

Proceeds from sales of fixed maturities classified as available for sale were $2.86 billion and $1.99 billion during the nine months ended September 30, 2021 and 2020, respectively. Gross gains of $56 million and $52 million and gross losses of $5 million and $3 million were realized on those sales during the nine months ended September 30, 2021 and 2020, respectively.

The cost and fair value of investments in equity securities were as follows:


							Fair
(at September 30, 2021, in millions)	Cost		Gross Gains		Gross Losses		Value
Public common stock	$	367	$	105	$	5	$	467
Non-redeemable preferred stock	31		11		—		42
Total	$	398	$	116	$	5	$	509

For the nine months ended September 30, 2021 and 2020, the Company recognized $45 million and $(14) million of net gains (losses) on equity securities still held as of September 30, 2021 and 2020, respectively.

The following tables summarize, for all fixed maturities classified as available for sale in an unrealized loss position at September 30, 2021 and December 31, 2020, the aggregate fair value and gross unrealized loss by length of time those securities have been continuously in an unrealized loss position. The fair value amounts reported in the tables are estimates that are prepared using the process described in note 4 herein and in note 4 of notes to the consolidated financial statements in the Company’s 2020 Annual Report. The Company also relies upon estimates of several factors in its review and evaluation of individual investments, using the process described in note 1 of notes to the consolidated financial statements in the Company’s 2020 Annual Report to determine whether a credit loss impairment exists.


	Less than 12 months				12 months or longer				Total
(at September 30, 2021, in millions)	Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses
Fixed maturities
U.S. Treasury securities and obligations of U.S. government and government agencies and authorities	$	1,804	$	20	$	5	$	—	$	1,809	$	20
Obligations of states, municipalities and political subdivisions	5,143		107		116		4		5,259		111
Debt securities issued by foreign governments	391		5		2		—		393		5
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities	233		1		1		—		234		1
All other corporate bonds	5,831		121		189		8		6,020		129

Total	$	13,402	$	254	$	313	$	12	$	13,715	$	266


	Less than 12 months				12 months or longer				Total
(at December 31, 2020, in millions)	Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses
Fixed maturities
U.S. Treasury securities and obligations of U.S. government and government agencies and authorities	$	92	$	—	$	—	$	—	$	92	$	—
Obligations of states, municipalities and political subdivisions	245		2		—		—		245		2
Debt securities issued by foreign governments	7		—		—		—		7		—
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities	20		—		1		—		21		—
All other corporate bonds	681		6		97		3		778		9
Total	$	1,045	$	8	$	98	$	3	$	1,143	$	11

The following tables present changes in the allowance for expected credit losses on fixed maturities classified as available for sale for the category of All Other Corporate Bonds (no other categories of fixed maturities currently have an allowance for expected credit losses):


	Fixed Maturities
	At and For the Three Months Ended September 30, 2021		At and For the Three Months Ended September 30, 2020
(in millions)	All Other Corporate Bonds		All Other Corporate Bonds

Balance, beginning of period	$	2	$	8
Additions for expected credit losses on securities where no credit losses were previously recognized	—		1
Additions (reductions) for expected credit losses on securities where credit losses were previously recognized	1		(3)
Reductions due to sales/defaults of credit-impaired securities	(1)		(2)
Reductions for impairments of securities which the Company intends to sell or more likely than not will be required to sell (1)	—		—
Balance, end of period	$	2	$	4

(1)Credit impairment charges recognized in net realized investment gains (losses) for each of the three months ended September 30, 2021 and 2020 included $0 million of credit losses on fixed maturity securities which the Company had the intent to sell. An allowance for expected credit losses was not previously recorded for these securities.


	Fixed Maturities
	At and For the Nine Months Ended September 30, 2021		At and For the Nine Months Ended September 30, 2020
(in millions)	All Other Corporate Bonds			All Other Corporate Bonds

Balance, beginning of period	$	2		$	—
Additions for expected credit losses on securities where no credit losses were previously recognized	1			9
Additions (reductions) for expected credit losses on securities where credit losses were previously recognized	—			(3)
Reductions due to sales/defaults of credit-impaired securities	(1)			(2)
Reductions for impairments of securities which the Company intends to sell or more likely than not will be required to sell (1)	—			—
Balance, end of period	$	2		$	4

(1)Credit impairment charges recognized in net realized investment gains (losses) for the nine months ended September 30, 2021 and 2020 included $0 million and $14 million, respectively, of credit losses on fixed maturity securities which the Company had the intent to sell. An allowance for expected credit losses was not previously recorded for these securities.

Total net credit impairment charges included in net realized investment gains (losses) in the consolidated statement of income were $1 million and $(4) million for the three months ended September 30, 2021 and 2020, respectively, and $1 million and $58 million for the nine months ended September 30, 2021 and 2020, respectively. Additionally, net realized investment gains (losses) in the first nine months of 2020 included $40 million of realized losses related to the other-than-temporary impairment of the carrying value of an equity method investment included in other investments. Credit losses related to the fixed maturity portfolio for both the three months and nine months ended September 30, 2021 and 2020 represented less than 1% of the fixed maturity portfolio on a pre-tax basis and less than 1% of shareholders’ equity on an after-tax basis.