Investments (Details 5) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	$ 93		$ 18		$ 164		$ 68
Realized - impairments	(8)		(10)		(19)		(41)
Fixed maturities [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	20		27		40		51
Realized - impairments	1		(12)		(5)		(49)
Change in unrealized	378		172		741		417
Equity securities [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	77		6		133		41
Realized - impairments	(9)		(2)		(19)		(2)
Change in unrealized	(18)		(75)		22		(77)
Mortgage Loans and Other Investments [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments			(15)		(3)		(22)
Realized - impairments							(4)
Other [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	(4)	[1]			(6)	[1]	(2)	[1]
Realized - impairments	2	[1]	4	[1]	5	[1]	14	[1]
Change in unrealized	(122)	[1]	(121)	[1]	(224)	[1]	(185)	[1]
Tax Effects [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	(33)		(6)		(58)		(24)
Realized - impairments	3		3		7		14
Change in unrealized	(84)		9		(189)		(54)
Noncontrolling Interests [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments					(1)		(1)
Change in unrealized	(4)		(2)		(7)		(4)
Marketable Securities [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	60		12		105		43
Realized - impairments	(5)		(7)		(12)		(27)
Change in unrealized	$ 150		$ (17)		$ 343		$ 97

[1] Primarily adjustments to deferred policy acquisition costs related to annuities.