Invested Assets (Details 3) (USD $) In Millions	Jun. 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	$ 3,462	$ 4,189
Investment securities, Continuous unrealized loss position, Less than 12 months, Gross unrealized depreciation	62	122
Investment securities, Continuous unrealized loss position, Twelve months or longer, Fair value	710	862
Investment securities, Continuous unrealized loss position, 12 months or longer, Gross unrealized depreciation	91	125
Investment securities, Continuous unrealized loss position, Fair value, Total	4,172	5,051
Investment securities, Continuous unrealized loss position, Gross unrealized depreciation, Total	153	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	108	111
Investment securities, Continuous unrealized loss position, Less than 12 months, Gross unrealized depreciation	3	3
Investment securities, Continuous unrealized loss position, Twelve months or longer, Fair value	47	45
Investment securities, Continuous unrealized loss position, 12 months or longer, Gross unrealized depreciation	4	6
Investment securities, Continuous unrealized loss position, Fair value, Total	155	156
Investment securities, Continuous unrealized loss position, Gross unrealized depreciation, Total	7	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	552	474
Investment securities, Continuous unrealized loss position, Less than 12 months, Gross unrealized depreciation	10	12
Investment securities, Continuous unrealized loss position, Twelve months or longer, Fair value	156	166
Investment securities, Continuous unrealized loss position, 12 months or longer, Gross unrealized depreciation	7	9
Investment securities, Continuous unrealized loss position, Fair value, Total	708	640
Investment securities, Continuous unrealized loss position, Gross unrealized depreciation, Total	17	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	1,120	990
Investment securities, Continuous unrealized loss position, Less than 12 months, Gross unrealized depreciation	10	12
Investment securities, Continuous unrealized loss position, Twelve months or longer, Fair value	42	27
Investment securities, Continuous unrealized loss position, 12 months or longer, Gross unrealized depreciation	2	1
Investment securities, Continuous unrealized loss position, Fair value, Total	1,162	1,017
Investment securities, Continuous unrealized loss position, Gross unrealized depreciation, Total	12	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	70	9
Investment securities, Continuous unrealized loss position, Less than 12 months, Gross unrealized depreciation	2	1
Investment securities, Continuous unrealized loss position, Twelve months or longer, Fair value	23	41
Investment securities, Continuous unrealized loss position, 12 months or longer, Gross unrealized depreciation	4	5
Investment securities, Continuous unrealized loss position, Fair value, Total	93	50
Investment securities, Continuous unrealized loss position, Gross unrealized depreciation, Total	6	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	45	38
Investment securities, Continuous unrealized loss position, Less than 12 months, Gross unrealized depreciation	1	1
Investment securities, Continuous unrealized loss position, Twelve months or longer, Fair value	0	0
Investment securities, Continuous unrealized loss position, 12 months or longer, Gross unrealized depreciation	0	0
Investment securities, Continuous unrealized loss position, Fair value, Total	45	38
Investment securities, Continuous unrealized loss position, Gross unrealized depreciation, Total	1	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	1,453	2,498
Investment securities, Continuous unrealized loss position, Less than 12 months, Gross unrealized depreciation	22	79
Investment securities, Continuous unrealized loss position, Twelve months or longer, Fair value	253	284
Investment securities, Continuous unrealized loss position, 12 months or longer, Gross unrealized depreciation	38	43
Investment securities, Continuous unrealized loss position, Fair value, Total	1,706	2,782
Investment securities, Continuous unrealized loss position, Gross unrealized depreciation, Total	60	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	1,895	1,622
Investment securities, Continuous unrealized loss position, Less than 12 months, Gross unrealized depreciation	26	29
Investment securities, Continuous unrealized loss position, Twelve months or longer, Fair value	268	279
Investment securities, Continuous unrealized loss position, 12 months or longer, Gross unrealized depreciation	17	21
Investment securities, Continuous unrealized loss position, Fair value, Total	2,163	1,901
Investment securities, Continuous unrealized loss position, Gross unrealized depreciation, Total	43	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	3,348	4,120
Investment securities, Continuous unrealized loss position, Less than 12 months, Gross unrealized depreciation	48	108
Investment securities, Continuous unrealized loss position, Twelve months or longer, Fair value	521	563
Investment securities, Continuous unrealized loss position, 12 months or longer, Gross unrealized depreciation	55	64
Investment securities, Continuous unrealized loss position, Fair value, Total	3,869	4,683
Investment securities, Continuous unrealized loss position, Gross unrealized depreciation, Total	103	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	114	69
Investment securities, Continuous unrealized loss position, Less than 12 months, Gross unrealized depreciation	14	14
Investment securities, Continuous unrealized loss position, Twelve months or longer, Fair value	189	299
Investment securities, Continuous unrealized loss position, 12 months or longer, Gross unrealized depreciation	36	61
Investment securities, Continuous unrealized loss position, Fair value, Total	303	368
Investment securities, Continuous unrealized loss position, Gross unrealized depreciation, Total	$ 50	$ 75