Fair Values of Financial Instruments (Tables)

6 Months Ended

Jun. 30, 2012

Fair Values of Financial Instruments [Abstract]

Carrying values and fair values of financial instruments

	June 30, 2012				December 31, 2011
	Carrying Value		Fair Value		Carrying Value		Fair Value
	(in millions)
Assets
Invested assets
Short term investments	$	2,012	$	2,012	$	1,893	$	1,893
Fixed maturities		37,513		37,513		37,184		37,184
Equity securities		1,583		1,583		1,512		1,512
Liabilities
Long term debt		3,575		4,281		3,575		4,085

Fair values of financial instruments categorized based upon the lowest level of input

	June 30, 2012
	Level 1		Level 2		Level 3		Total
	(in millions)
Assets
Short term investments	$	115	$	1,897	$	—	$	2,012
Fixed maturities
Tax exempt		—		20,254		6		20,260
Taxable
U.S. government and government agency and authority obligations		—		1,076		—		1,076
Corporate bonds		—		6,935		149		7,084
Foreign government and government agency obligations		—		6,660		—		6,660
Residential mortgage-backed securities		—		600		10		610
Commercial mortgage-backed securities		—		1,823		—		1,823
		—		17,094		159		17,253
Total fixed maturities		—		37,348		165		37,513
Equity securities		1,575		—		8		1,583
	$	1,690	$	39,245	$	173	$	41,108
Liabilities
Long term debt	$	—	$	4,281	$	—	$	4,281

	December 31, 2011
	Level 1		Level 2		Level 3		Total
	(in millions)
Assets
Short term investments	$	117	$	1,776	$	—	$	1,893
Fixed maturities
Tax exempt		—		20,203		8		20,211
Taxable
U.S. government and government agency and authority obligations		—		868		—		868
Corporate bonds		—		6,313		152		6,465
Foreign government and government agency obligations		—		6,820		3		6,823
Residential mortgage-backed securities		—		845		10		855
Commercial mortgage-backed securities		—		1,962		—		1,962
		—		16,808		165		16,973
Total fixed maturities		—		37,011		173		37,184
Equity securities		1,504		—		8		1,512
	$	1,621	$	38,787	$	181	$	40,589
Liabilities
Long term debt	$	—	$	4,085	$	—	$	4,085