Invested Assets and Related Income (Details 4) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Components of unrealized appreciation or depreciation of investments [Abstract]
Fixed maturities, Gross unrealized appreciation	$ 2,495	$ 1,630
Fixed maturities, Gross unrealized depreciation	73	172
Fixed maturities, Unrealized appreciation (depreciation), Net	2,422	1,458
Equity securities, Gross unrealized appreciation	319	340
Equity securities, Gross unrealized depreciation	71	75
Equity securities, Unrealized appreciation (depreciation), Net	248	265
Total fixed maturities and equity securities, Unrealized appreciation (depreciation), Net	2,670	1,723
Deferred income tax liability	934	603
Total fixed maturities and equity securities, Unrealized appreciation (depreciation), Net of tax	$ 1,736	$ 1,120