Investments (Details 3) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Net Investment Income:
Investment income, before expense	$ 1,038	$ 1,076	$ 2,069	$ 2,136
Investment expense	(54)	(50)	(102)	(99)
Net investment income	984	1,026	1,967	2,037
Fixed income securities
Net Investment Income:
Investment income, before expense	740	818	1,502	1,624
Equity securities
Net Investment Income:
Investment income, before expense	39	24	64	45
Mortgage loans
Net Investment Income:
Investment income, before expense	93	92	191	185
Limited partnership interests
Net Investment Income:
Investment income, before expense	126	107	233	216
Short-term investments
Net Investment Income:
Investment income, before expense	1	1	3	2
Other
Net Investment Income:
Investment income, before expense	$ 39	$ 34	$ 76	$ 64