Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2021

Fair Value Disclosures [Abstract]

Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured on a recurring basis [Table Text Block]

The following tables present the level within the fair value hierarchy at which the Company’s financial assets and financial liabilities are measured on a recurring basis.

(at December 31, 2021, in millions)	Total		Level 1		Level 2		Level 3
Invested assets:
Fixed maturities
U.S. Treasury securities and obligations of U.S. government and government agencies and authorities	$	3,562	$	3,562	$	—	$	—
Obligations of states, municipalities and political subdivisions	36,862		—		36,858		4
Debt securities issued by foreign governments	1,041		—		1,041		—
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities	1,817		—		1,762		55
All other corporate bonds	34,514		—		34,325		189
Redeemable preferred stock	14		—		14		—
Total fixed maturities	77,810		3,562		74,000		248
Equity securities
Common stock	827		509		—		318
Non-redeemable preferred stock	66		21		20		25
Total equity securities	893		530		20		343
Other investments	23		18		—		5
Total	$	78,726	$	4,110	$	74,020	$	596
Other liabilities	$	3	$	—	$	—	$	3

(at December 31, 2020, in millions)	Total		Level 1		Level 2		Level 3
Invested assets:
Fixed maturities
U.S. Treasury securities and obligations of U.S. government and government agencies and authorities	$	2,149	$	2,149	$	—	$	—
Obligations of states, municipalities and political subdivisions	36,360		—		36,349		11
Debt securities issued by foreign governments	1,054		—		1,054		—
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities	2,361		—		2,361		—
All other corporate bonds	32,054		—		31,899		155
Redeemable preferred stock	25		3		22		—
Total fixed maturities	74,003		2,152		71,685		166
Equity securities
Common stock	416		410		—		6
Non-redeemable preferred stock	68		18		25		25
Total equity securities	484		428		25		31
Other investments	21		17		—		4
Total	$	74,508	$	2,597	$	71,710	$	201
Other liabilities	$	5	$	—	$	—	$	5

Changes in the Level 3 fair value category [Table Text Block]

The following tables present the changes in the Level 3 fair value category for the years ended December 31, 2021 and 2020.

(in millions)	Fixed Maturities		Equity Securities		Other Investments		Total
Balance at December 31, 2020	$	166	$	31	$	4	$	201
Total realized and unrealized investment gains (losses):
Reported in net realized investment gains (1)	(1)		5		1		5
Reported in increases in other comprehensive income (loss)	(3)		—		—		(3)
Purchases, sales and settlements/maturities:
Purchases	227		307		—		534
Sales	—		—		—		—
Settlements/maturities	(48)		—		—		(48)
Gross transfers into Level 3	—		—		—		—
Gross transfers out of Level 3	(93)		—		—		(93)
Balance at December 31, 2021	$	248	$	343	$	5	$	596
Amount of total realized investment gains (losses) for the period included in the consolidated statement of income attributable to changes in the fair value of assets still held at the reporting date	$	—	$	5	$	1	$	6

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(1)Includes impairments on investments held at the end of the period as well as amortization on fixed maturities.

(in millions)	Fixed Maturities		Equity Securities		Other Investments		Total
Balance at December 31, 2019	$	101	$	13	$	7	$	121
Total realized and unrealized investment gains (losses):
Reported in net realized investment gains (1)	(1)		2		(2)		(1)
Reported in increases in other comprehensive income (loss)	2		—		—		2
Purchases, sales and settlements/maturities:
Purchases	79		16		—		95
Sales	—		—		(1)		(1)
Settlements/maturities	(15)		—		—		(15)
Gross transfers into Level 3	3		—		—		3
Gross transfers out of Level 3	(3)		—		—		(3)
Balance at December 31, 2020	$	166	$	31	$	4	$	201
Amount of total realized investment gains (losses) for the period included in the consolidated statement of income attributable to changes in the fair value of assets still held at the reporting date	$	—	$	2	$	(2)	$	—

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(1)Includes impairments on investments held at the end of the period as well as amortization on fixed maturities.

Carrying value and fair value of the Company's financial assets and financial liabilities disclosed, but not carried, at fair value, and the level within the fair value hierarchy at which such assets and liabilities are categorized [Table Text Block]

The following tables present the carrying value and fair value of the Company’s financial assets and financial liabilities disclosed, but not carried, at fair value, and the level within the fair value hierarchy at which such assets and liabilities are categorized.

(at December 31, 2021, in millions)	Carrying Value		Fair Value		Level 1		Level 2		Level 3
Financial assets:
Short-term securities	$	3,836	$	3,836	$	1,163	$	2,615	$	58
Financial liabilities:
Debt	$	7,190	$	9,085	$	—	$	9,085	$	—
Commercial paper	100		100		—		100		—

(at December 31, 2020, in millions)	Carrying Value		Fair Value		Level 1		Level 2		Level 3
Financial assets:
Short-term securities	$	5,511	$	5,511	$	630	$	4,829	$	52
Financial liabilities:
Debt	$	6,450	$	8,976	$	—	$	8,976	$	—
Commercial paper	100		100		—		100		—