Fair Value Measurements (tables)

12 Months Ended

Dec. 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 on a recurring basis [Table Text Block]

(at December 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	$	2,076	$	2,076	$	—	$	—
Obligations of states, municipalities and political subdivisions		30,915		—		30,910		5
Debt securities issued by foreign governments		1,509		—		1,509		—
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities		2,410		—		2,371		39
All other corporate bonds		25,689		11		25,518		160
Redeemable preferred stock		95		3		92		—
Total fixed maturities		62,694		2,090		60,400		204
Equity securities
Public common stock		339		339		—		—
Non-redeemable preferred stock		114		45		69		—
Total equity securities		453		384		69		—
Other investments		57		19		—		38
Total	$	63,204	$	2,493	$	60,469	$	242

(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

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

(in millions)	Fixed Maturities			Other Investments			Total
Balance at December 31, 2016	$	184		$	36		$	220
Total realized and unrealized investment gains (losses):
Reported in net realized investment gains(1)		—			(1	)		(1	)
Reported in increases in other comprehensive income (loss)		1			3			4
Purchases, sales and settlements/maturities:
Purchases		312			—			312
Sales		(2	)		—			(2	)
Settlements/maturities		(47	)		—			(47	)
Gross transfers into Level 3		21			—			21
Gross transfers out of Level 3		(265	)		—			(265	)
Balance at December 31, 2017	$	204		$	38		$	242
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	$	—		$	(1	)	$	(1	)

(1)

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

(in millions)	Fixed Maturities			Other Investments			Total
Balance at December 31, 2015	$	218		$	38		$	256
Total realized and unrealized investment gains (losses):
Reported in net realized investment gains(1)		3			5			8
Reported in increases in other comprehensive income (loss)		2			3			5
Purchases, sales and settlements/maturities:
Purchases		123			—			123
Sales		(19	)		(10	)		(29	)
Settlements/maturities		(66	)		—			(66	)
Gross transfers into Level 3		19			—			19
Gross transfers out of Level 3		(96	)		—			(96	)
Balance at December 31, 2016	$	184		$	36		$	220
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	)

(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 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 December 31, 2017, in millions)	Carrying Value		Fair Value		Level 1		Level 2		Level 3
Financial assets:
Short-term securities	$	4,895	$	4,895	$	1,238	$	3,622	$	35
Financial liabilities:
Debt	$	6,471	$	7,702	$	—	$	7,702	$	—
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		—