Investments (Details 4) (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 capital gains and losses by asset type
Realized capital gains and losses	$ (57)	$ 218	$ (72)	$ 335
Fixed income securities
Realized capital gains and losses by asset type
Realized capital gains and losses	(60)	429	(116)	494
Mortgage loans
Realized capital gains and losses by asset type
Realized capital gains and losses	(3)	(28)	5	(33)
Equity securities
Realized capital gains and losses by asset type
Realized capital gains and losses	(1)		(1)	14
Limited partnership interests
Realized capital gains and losses by asset type
Realized capital gains and losses		11	1	63
Derivatives
Realized capital gains and losses by asset type
Realized capital gains and losses	8	(186)	34	(207)
Other
Realized capital gains and losses by asset type
Realized capital gains and losses	$ (1)	$ (8)	$ 5	$ 4