Invested Assets (Details 3) (USD $) In Millions	Sep. 30, 2011	Dec. 31, 2010
Fair value and gross unrealized depreciation of investments in an unrealized loss position [Abstract]
Investment securities, Continuous unrealized loss position, Less than twelve months, Fair value	$ 2,057	$ 4,189
Investment securities, Continuous unrealized loss position, Less than twelve months, Gross unrealized depreciation	106	122
Investment securities, Continuous unrealized loss position, Twelve months or longer, Fair value	721	862
Investment securities, Continuous unrealized loss position, Twelve months or longer, Gross unrealized depreciation	119	125
Investment securities, Continuous unrealized loss position, Fair value, Total	2,778	5,051
Investment securities, Continuous unrealized loss position, Gross unrealized depreciation, Total	225	247
U.S. Government and government agency and authority obligations [Member] | Taxable [Member] | Fixed Maturities [Member]
Fair value and gross unrealized depreciation of investments in an unrealized loss position [Abstract]
Investment securities, Continuous unrealized loss position, Less than twelve months, Fair value	62	111
Investment securities, Continuous unrealized loss position, Less than twelve months, Gross unrealized depreciation	1	3
Investment securities, Continuous unrealized loss position, Twelve months or longer, Fair value	49	45
Investment securities, Continuous unrealized loss position, Twelve months or longer, Gross unrealized depreciation	1	6
Investment securities, Continuous unrealized loss position, Fair value, Total	111	156
Investment securities, Continuous unrealized loss position, Gross unrealized depreciation, Total	2	9
Corporate bonds [Member] | Taxable [Member] | Fixed Maturities [Member]
Fair value and gross unrealized depreciation of investments in an unrealized loss position [Abstract]
Investment securities, Continuous unrealized loss position, Less than twelve months, Fair value	753	474
Investment securities, Continuous unrealized loss position, Less than twelve months, Gross unrealized depreciation	23	12
Investment securities, Continuous unrealized loss position, Twelve months or longer, Fair value	176	166
Investment securities, Continuous unrealized loss position, Twelve months or longer, Gross unrealized depreciation	8	9
Investment securities, Continuous unrealized loss position, Fair value, Total	929	640
Investment securities, Continuous unrealized loss position, Gross unrealized depreciation, Total	31	21
Foreign government and government agency obligations [Member] | Taxable [Member] | Fixed Maturities [Member]
Fair value and gross unrealized depreciation of investments in an unrealized loss position [Abstract]
Investment securities, Continuous unrealized loss position, Less than twelve months, Fair value	486	990
Investment securities, Continuous unrealized loss position, Less than twelve months, Gross unrealized depreciation	5	12
Investment securities, Continuous unrealized loss position, Twelve months or longer, Fair value	43	27
Investment securities, Continuous unrealized loss position, Twelve months or longer, Gross unrealized depreciation	1	1
Investment securities, Continuous unrealized loss position, Fair value, Total	529	1,017
Investment securities, Continuous unrealized loss position, Gross unrealized depreciation, Total	6	13
Residential Mortgage-Backed Securities [Member] | Taxable [Member] | Fixed Maturities [Member]
Fair value and gross unrealized depreciation of investments in an unrealized loss position [Abstract]
Investment securities, Continuous unrealized loss position, Less than twelve months, Fair value	69	9
Investment securities, Continuous unrealized loss position, Less than twelve months, Gross unrealized depreciation	1	1
Investment securities, Continuous unrealized loss position, Twelve months or longer, Fair value	21	41
Investment securities, Continuous unrealized loss position, Twelve months or longer, Gross unrealized depreciation	4	5
Investment securities, Continuous unrealized loss position, Fair value, Total	90	50
Investment securities, Continuous unrealized loss position, Gross unrealized depreciation, Total	5	6
Commercial Mortgage-Backed Securities [Member] | Taxable [Member] | Fixed Maturities [Member]
Fair value and gross unrealized depreciation of investments in an unrealized loss position [Abstract]
Investment securities, Continuous unrealized loss position, Less than twelve months, Fair value	73	38
Investment securities, Continuous unrealized loss position, Less than twelve months, Gross unrealized depreciation	1	1
Investment securities, Continuous unrealized loss position, Twelve months or longer, Fair value	2	0
Investment securities, Continuous unrealized loss position, Twelve months or longer, Gross unrealized depreciation	1	0
Investment securities, Continuous unrealized loss position, Fair value, Total	75	38
Investment securities, Continuous unrealized loss position, Gross unrealized depreciation, Total	2	1
Tax Exempt [Member] | Fixed Maturities [Member]
Fair value and gross unrealized depreciation of investments in an unrealized loss position [Abstract]
Investment securities, Continuous unrealized loss position, Less than twelve months, Fair value	292	2,498
Investment securities, Continuous unrealized loss position, Less than twelve months, Gross unrealized depreciation	3	79
Investment securities, Continuous unrealized loss position, Twelve months or longer, Fair value	270	284
Investment securities, Continuous unrealized loss position, Twelve months or longer, Gross unrealized depreciation	39	43
Investment securities, Continuous unrealized loss position, Fair value, Total	562	2,782
Investment securities, Continuous unrealized loss position, Gross unrealized depreciation, Total	42	122
Taxable [Member] | Fixed Maturities [Member]
Fair value and gross unrealized depreciation of investments in an unrealized loss position [Abstract]
Investment securities, Continuous unrealized loss position, Less than twelve months, Fair value	1,443	1,622
Investment securities, Continuous unrealized loss position, Less than twelve months, Gross unrealized depreciation	31	29
Investment securities, Continuous unrealized loss position, Twelve months or longer, Fair value	291	279
Investment securities, Continuous unrealized loss position, Twelve months or longer, Gross unrealized depreciation	15	21
Investment securities, Continuous unrealized loss position, Fair value, Total	1,734	1,901
Investment securities, Continuous unrealized loss position, Gross unrealized depreciation, Total	46	50
Fixed Maturities [Member]
Fair value and gross unrealized depreciation of investments in an unrealized loss position [Abstract]
Investment securities, Continuous unrealized loss position, Less than twelve months, Fair value	1,735	4,120
Investment securities, Continuous unrealized loss position, Less than twelve months, Gross unrealized depreciation	34	108
Investment securities, Continuous unrealized loss position, Twelve months or longer, Fair value	561	563
Investment securities, Continuous unrealized loss position, Twelve months or longer, Gross unrealized depreciation	54	64
Investment securities, Continuous unrealized loss position, Fair value, Total	2,296	4,683
Investment securities, Continuous unrealized loss position, Gross unrealized depreciation, Total	88	172
Equity Securities [Member]
Fair value and gross unrealized depreciation of investments in an unrealized loss position [Abstract]
Investment securities, Continuous unrealized loss position, Less than twelve months, Fair value	322	69
Investment securities, Continuous unrealized loss position, Less than twelve months, Gross unrealized depreciation	72	14
Investment securities, Continuous unrealized loss position, Twelve months or longer, Fair value	160	299
Investment securities, Continuous unrealized loss position, Twelve months or longer, Gross unrealized depreciation	65	61
Investment securities, Continuous unrealized loss position, Fair value, Total	482	368
Investment securities, Continuous unrealized loss position, Gross unrealized depreciation, Total	$ 137	$ 75