Investments (Details 4) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Realized capital gains and losses by asset type
Realized capital gains and losses	$ 131	$ 168
Fixed income securities
Realized capital gains and losses by asset type
Realized capital gains and losses	72	(29)
Equity securities
Realized capital gains and losses by asset type
Realized capital gains and losses	29	159
Mortgage loans
Realized capital gains and losses by asset type
Realized capital gains and losses	31	(1)
Limited partnership interests
Realized capital gains and losses by asset type
Realized capital gains and losses	5	10
Derivatives
Realized capital gains and losses by asset type
Realized capital gains and losses	(4)	21
Other
Realized capital gains and losses by asset type
Realized capital gains and losses	$ (2)	$ 8