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	$ 995	$ 1,038	$ 3,131	$ 3,134
Investment expense	(55)	(44)	(154)	(138)
Net investment income	940	994	2,977	2,996
Fixed income securities
Net Investment Income:
Investment income, before expense	817	862	2,441	2,661
Equity securities
Net Investment Income:
Investment income, before expense	29	23	74	76
Mortgage loans
Net Investment Income:
Investment income, before expense	92	91	277	267
Limited partnership interests
Net Investment Income:
Investment income, before expense	22	33	238	61
Short-term investments
Net Investment Income:
Investment income, before expense	2	2	4	5
Other
Net Investment Income:
Investment income, before expense	$ 33	$ 27	$ 97	$ 64