Fair Value Measurements (Details 8) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Fixed Maturities, FVO [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value of assets accounted for using fair value option	$ 1,355		$ 1,328
ABS [Member] | Fixed Maturities, FVO [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value of assets accounted for using fair value option	65		65
Commercial Real Estate collateralized debt obligation [Member] | Fixed Maturities, FVO [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value of assets accounted for using fair value option	247		225
Corporate [Member] | Fixed Maturities, FVO [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value of assets accounted for using fair value option	281		272
Foreign Government Debt Securities [Member] | Fixed Maturities, FVO [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value of assets accounted for using fair value option	762		766
Credit-linked notes [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value of liabilities accounted for using fair value option	$ 43	[1]	$ 9	[1]

[1] As of September 30, 2012 and December 31, 2011, the outstanding principal balance of the notes was $243.