Invested Assets (Details 2) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Components of unrealized appreciation or depreciation of investments [Abstract]
Fixed maturities, Gross unrealized appreciation	$ 2,582	$ 2,495
Fixed maturities, Gross unrealized depreciation	44	73
Fixed maturities, Unrealized appreciation (depreciation), Net	2,538	2,422
Equity securities, Gross Unrealized Appreciation	362	319
Equity securities, Gross unrealized depreciation	40	71
Equity securities, Unrealized appreciation (depreciation), Net	322	248
Total fixed maturities and equity securities, Unrealized appreciation (depreciation), Net	2,860	2,670
Deferred income tax liability	1,001	934
Total fixed maturities and equity securities, Unrealized appreciation (depreciation), Net of tax	$ 1,859	$ 1,736