Fair Value Measurements (tables)

3 Months Ended

Mar. 31, 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 [Table Text Block]

(at March 31, 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	$	2,049	$	2,049	$	—	$	—
Obligations of states, municipalities and political subdivisions	31,960		—		31,956		4
Debt securities issued by foreign governments	1,590		—		1,590		—
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities	1,780		—		1,692		88
All other corporate bonds	23,795		5		23,620		170
Redeemable preferred stock	94		3		91		—
Total fixed maturities	61,268		2,057		58,949		262
Equity securities
Public common stock	619		619		—		—
Non-redeemable preferred stock	132		67		65		—
Total equity securities	751		686		65		—
Other investments	53		17		—		36
Total	$	62,072	$	2,760	$	59,014	$	298

(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 March 31, 2017, in millions)	Carrying Value		Fair Value		Level 1		Level 2		Level 3
Financial assets:
Short-term securities	$	4,817	$	4,817	$	991	$	3,791	$	35
Financial liabilities:
Debt	$	6,338	$	7,306	$	—	$	7,306	$	—
Commercial paper	$	100	$	100	$	—	$	100	$	—

(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	$	—