Fair Value Measurements (Details 8) (USD $) In Millions, unless otherwise specified	Mar. 31, 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	$ 1,291	$ 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
CRE CDOs [Member] | Fixed Maturities, FVO [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value of assets accounted for using fair value option	240	225
Corporate [Member] | Fixed Maturities, FVO [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value of assets accounted for using fair value option	270	272
Foreign government [Member] | Fixed Maturities, FVO [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value of assets accounted for using fair value option	716	766
Credit-linked notes [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value of liabilities accounted for using fair value option	$ 21	$ 9