Investments (Details 5) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	$ 42		$ 23		$ 99		$ 71
Realized - impairments	(1)		(7)		(1)		(11)
Fixed maturities [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	8		6		27		20
Realized - impairments	0		0		0		(4)
Change in unrealized	(725)		231		(740)		363
Equity securities [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	33		21		71		56
Realized - impairments	0		(8)		0		(10)
Change in unrealized	(13)		(30)		54		40
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	1		(4)		2		(3)
Realized - impairments	(1)				(1)		0
Other [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	0	[1]	0	[1]	(1)	[1]	(2)	[1]
Realized - impairments	0	[1]	1	[1]	0	[1]	3	[1]
Change in unrealized	319	[1]	(100)	[1]	333	[1]	(102)	[1]
Tax Effects [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	(15)		(8)		(35)		(25)
Realized - impairments	0		3		0		4
Change in unrealized	147		(35)		124		(105)
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)
Change in unrealized	7		0		6		(3)
Marketable Securities [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	27		14		63		45
Realized - impairments	(1)		(4)		(1)		(7)
Change in unrealized	$ (265)		$ 66		$ (223)		$ 193

[1] Primarily adjustments to deferred policy acquisition costs and reserves related to annuities and long-term care business.