Fair Value Measurements (tables)

9 Months Ended

Sep. 30, 2017

Fair Value Measurements disclosure

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

(at September 30, 2017, 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	$	2,068	$	2,068	$	—	$	—
Obligations of states, municipalities and political subdivisions	31,175		18		31,153		4
Debt securities issued by foreign governments	1,565		—		1,565		—
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities	2,173		—		2,143		30
All other corporate bonds	25,080		2		24,914		164
Redeemable preferred stock	96		3		93		—
Total fixed maturities	62,157		2,091		59,868		198
Equity securities
Public common stock	470		470		—		—
Non-redeemable preferred stock	131		68		63		—
Total equity securities	601		538		63		—
Other investments	56		18		—		38
Total	$	62,814	$	2,647	$	59,931	$	236

(at December 31, 2016, 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	$	2,035	$	2,035	$	—	$	—
Obligations of states, municipalities and political subdivisions	31,910		—		31,898		12
Debt securities issued by foreign governments	1,662		—		1,662		—
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities	1,708		—		1,704		4
All other corporate bonds	23,107		—		22,939		168
Redeemable preferred stock	93		3		90		—
Total fixed maturities	60,515		2,038		58,293		184
Equity securities
Public common stock	603		603		—		—
Non-redeemable preferred stock	129		51		78		—
Total equity securities	732		654		78		—
Other investments	53		17		—		36
Total	$	61,300	$	2,709	$	58,371	$	220

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

(at September 30, 2017, in millions)	Carrying Value		Fair Value		Level 1		Level 2		Level 3
Financial assets:
Short-term securities	$	5,859	$	5,859	$	1,830	$	3,995	$	34
Financial liabilities:
Debt	$	6,921	$	8,042	$	—	$	8,042	$	—

(at December 31, 2016, in millions)	Carrying Value		Fair Value		Level 1		Level 2		Level 3
Financial assets:
Short-term securities	$	4,865	$	4,865	$	1,223	$	3,607	$	35
Financial liabilities:
Debt	$	6,337	$	7,262	$	—	$	7,262	$	—
Commercial paper	$	100	$	100	$	—	$	100	$	—