Fair Value Measurements (Details 7) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Fair Value, Option, Quantitative Disclosures [Line Items]
Changes in fair value of assets and liabilities accounted for using the fair value option	$ 23	$ 1	$ (17)	$ 38
Corporate [Member] | Fixed Maturities, FVO [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Changes in fair value of assets and liabilities accounted for using the fair value option	6	(3)	6	11
Commercial Real Estate collateralized debt obligation [Member] | Fixed Maturities, FVO [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Changes in fair value of assets and liabilities accounted for using the fair value option	18	(60)	27	(41)
Foreign Government Debt Securities [Member] | Fixed Maturities, FVO [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Changes in fair value of assets and liabilities accounted for using the fair value option	13	33	(16)	44
Credit Linked Notes [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Changes in fair value of assets and liabilities accounted for using the fair value option	$ (14)	$ 31	$ (34)	$ 24