Investments (Details 3) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Net Investment Income:
Investment income, before expense	$ 1,060	$ 1,031
Investment expense	(49)	(49)
Net investment income	1,011	982
Fixed income securities
Net Investment Income:
Investment income, before expense	806	900
Equity securities
Net Investment Income:
Investment income, before expense	21	19
Mortgage loans
Net Investment Income:
Investment income, before expense	93	89
Limited partnership interests
Net Investment Income:
Investment income, before expense	109	10
Short-term investments
Net Investment Income:
Investment income, before expense	1	2
Other
Net Investment Income:
Investment income, before expense	$ 30	$ 11