Investments (Details 5) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	$ 57		$ 48
Realized - impairments			(4)
Fixed maturities [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	19		14
Realized - impairments	0		(4)
Change in unrealized	(15)		132
Equity securities [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	38		35
Realized - impairments	0		(2)
Change in unrealized	67		70
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		1
Realized - impairments
Other [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	(1)	[1]	(2)	[1]
Realized - impairments	0	[1]	2	[1]
Change in unrealized	14	[1]	(2)	[1]
Tax Effects [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	(20)		(17)
Realized - impairments	0		1
Change in unrealized	(23)		(70)
Noncontrolling Interests [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	(1)
Change in unrealized	(1)		(3)
Marketable Securities [Member]
Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments
Realized before impairments	36		31
Realized - impairments	0		(3)
Change in unrealized	$ 42		$ 127

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