Investments (Details 5) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	$ 23	$ 40	$ 71	$ 50
Realized - impairments	(7)	(21)	(11)	(31)
Fixed maturities [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	6	11	20	24
Realized - impairments		(26)	(4)	(37)
Change in unrealized	231	208	363	245
Equity securities [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	21	34	56	35
Realized - impairments	(8)		(10)
Change in unrealized	(30)	(15)	40	(2)
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	(4)	(5)	(3)	(7)
Realized - impairments		(1)		(4)
Other [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments			(2)	(2)
Realized - impairments	1	6	3	10
Change in unrealized	(100)	(42)	(102)	(64)
Tax Effects [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	(8)	(15)	(25)	(18)
Realized - impairments	3	8	4	11
Change in unrealized	(35)	(53)	(105)	(63)
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)	(1)	(1)
Change in unrealized		(2)	(3)	(2)
Marketable Securities [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	14	24	45	31
Realized - impairments	(4)	(13)	(7)	(20)
Change in unrealized	$ 66	$ 96	$ 193	$ 114