Investments (Details 3) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Net Investment Income:
Investment income, before expense	$ 1,076	$ 1,065	$ 2,136	$ 2,096
Investment expense	(50)	(45)	(99)	(94)
Net investment income	1,026	1,020	2,037	2,002
Fixed income securities
Net Investment Income:
Investment income, before expense	818	899	1,624	1,799
Equity securities
Net Investment Income:
Investment income, before expense	24	34	45	53
Mortgage loans
Net Investment Income:
Investment income, before expense	92	87	185	176
Limited partnership interests
Net Investment Income:
Investment income, before expense	107	18	216	28
Short-term investments
Net Investment Income:
Investment income, before expense	1	1	2	3
Other
Net Investment Income:
Investment income, before expense	$ 34	$ 26	$ 64	$ 37