Investments (Details 4) (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 capital gains and losses by asset type
Realized capital gains and losses	$ 27	$ 57	$ 195	$ 153
Fixed income securities
Realized capital gains and losses by asset type
Realized capital gains and losses	6	39	(23)	12
Equity securities
Realized capital gains and losses by asset type
Realized capital gains and losses	13	15	172	137
Mortgage loans
Realized capital gains and losses by asset type
Realized capital gains and losses	9	(3)	8	(9)
Limited partnership interests
Realized capital gains and losses by asset type
Realized capital gains and losses	3	53	13	121
Derivatives
Realized capital gains and losses by asset type
Realized capital gains and losses	7	(53)	28	(120)
Other
Realized capital gains and losses by asset type
Realized capital gains and losses	$ (11)	$ 6	$ (3)	$ 12