Investments (Details 3) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Net investment income
Investment income, before expense	$ 650	$ 687	$ 2,031	$ 2,074
Investment expense	(29)	(26)	(87)	(78)
Net investment income	621	661	1,944	1,996
Fixed income securities
Net investment income
Investment income, before expense	521	558	1,567	1,730
Mortgage loans
Net investment income
Investment income, before expense	86	85	256	258
Equity securities
Net investment income
Investment income, before expense	2	3	5	5
Limited partnership interests
Net investment income
Investment income, before expense	11	18	117	34
Short-term investments
Net investment income
Investment income, before expense	1	1	1	2
Other
Net investment income
Investment income, before expense	$ 29	$ 22	$ 85	$ 45