Invested Assets (Details 3) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
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	$ 1,100	$ 1,430
Investment securities, Continuous unrealized loss position, Less than twelve months, Gross Unrealized Depreciation	37	65
Investment securities, Continuous unrealized loss position, Twelve months or longer, Fair Value	318	676
Investment securities, Continuous unrealized loss position, Twelve months or longer, Gross Unrealized Depreciation	47	79
Investment securities, Continuous unrealized loss position, Fair Value, Total	1,418	2,106
Investment securities, Continuous unrealized loss position, Gross Unrealized Depreciation, Total	84	144
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	898	1,199
Investment securities, Continuous unrealized loss position, Less than twelve months, Gross Unrealized Depreciation	8	20
Investment securities, Continuous unrealized loss position, Twelve months or longer, Fair Value	277	477
Investment securities, Continuous unrealized loss position, Twelve months or longer, Gross Unrealized Depreciation	36	53
Investment securities, Continuous unrealized loss position, Fair Value, Total	1,175	1,676
Investment securities, Continuous unrealized loss position, Gross Unrealized Depreciation, Total	44	73
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	202	231
Investment securities, Continuous unrealized loss position, Less than twelve months, Gross Unrealized Depreciation	29	45
Investment securities, Continuous unrealized loss position, Twelve months or longer, Fair Value	41	199
Investment securities, Continuous unrealized loss position, Twelve months or longer, Gross Unrealized Depreciation	11	26
Investment securities, Continuous unrealized loss position, Fair Value, Total	243	430
Investment securities, Continuous unrealized loss position, Gross Unrealized Depreciation, Total	40	71
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	302	81
Investment securities, Continuous unrealized loss position, Less than twelve months, Gross Unrealized Depreciation	2	1
Investment securities, Continuous unrealized loss position, Twelve months or longer, Fair Value	141	240
Investment securities, Continuous unrealized loss position, Twelve months or longer, Gross Unrealized Depreciation	26	36
Investment securities, Continuous unrealized loss position, Fair Value, Total	443	321
Investment securities, Continuous unrealized loss position, Gross Unrealized Depreciation, Total	28	37
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	596	1,118
Investment securities, Continuous unrealized loss position, Less than twelve months, Gross Unrealized Depreciation	6	19
Investment securities, Continuous unrealized loss position, Twelve months or longer, Fair Value	136	237
Investment securities, Continuous unrealized loss position, Twelve months or longer, Gross Unrealized Depreciation	10	17
Investment securities, Continuous unrealized loss position, Fair Value, Total	732	1,355
Investment securities, Continuous unrealized loss position, Gross Unrealized Depreciation, Total	16	36
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	75	19
Investment securities, Continuous unrealized loss position, Less than twelve months, Gross Unrealized Depreciation		1
Investment securities, Continuous unrealized loss position, Twelve months or longer, Fair Value	19	18
Investment securities, Continuous unrealized loss position, Twelve months or longer, Gross Unrealized Depreciation	1	1
Investment securities, Continuous unrealized loss position, Fair Value, Total	94	37
Investment securities, Continuous unrealized loss position, Gross Unrealized Depreciation, Total	1	2
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	335	489
Investment securities, Continuous unrealized loss position, Less than twelve months, Gross Unrealized Depreciation	4	14
Investment securities, Continuous unrealized loss position, Twelve months or longer, Fair Value	68	176
Investment securities, Continuous unrealized loss position, Twelve months or longer, Gross Unrealized Depreciation	6	10
Investment securities, Continuous unrealized loss position, Fair Value, Total	403	665
Investment securities, Continuous unrealized loss position, Gross Unrealized Depreciation, Total	10	24
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	111	499
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	13	21
Investment securities, Continuous unrealized loss position, Twelve months or longer, Gross Unrealized Depreciation		1
Investment securities, Continuous unrealized loss position, Fair Value, Total	124	520
Investment securities, Continuous unrealized loss position, Gross Unrealized Depreciation, Total	1	2
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	6	77
Investment securities, Continuous unrealized loss position, Less than twelve months, Gross Unrealized Depreciation		2
Investment securities, Continuous unrealized loss position, Twelve months or longer, Fair Value	35	22
Investment securities, Continuous unrealized loss position, Twelve months or longer, Gross Unrealized Depreciation	3	5
Investment securities, Continuous unrealized loss position, Fair Value, Total	41	99
Investment securities, Continuous unrealized loss position, Gross Unrealized Depreciation, Total	3	7
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	69	34
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	1
Investment securities, Continuous unrealized loss position, Twelve months or longer, Gross Unrealized Depreciation
Investment securities, Continuous unrealized loss position, Fair Value, Total	70	34
Investment securities, Continuous unrealized loss position, Gross Unrealized Depreciation, Total	$ 1	$ 1