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	$ 22	$ (3)	$ (18)	$ 36
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	17	(64)	26	(43)
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