Investments and Derivative Instruments (Details 19) (USD $) In Millions, unless otherwise specified	9 Months Ended		12 Months Ended
	Sep. 30, 2012		Dec. 31, 2011
Derivative [Line Items]
Notional Amount	$ 173,376		$ 141,436
Fair Value	(58)		(458)
Credit [Member]
Derivative [Line Items]
Notional Amount	8,383	[1]	7,046	[1]
Fair Value	91		(305)
Offsetting Notional Amount	4,714	[2]	4,094	[2]
Offsetting Fair Value	40	[2]	107	[2]
Corporate Credit/Foreign Gov. [Member] | Single Name Credit Default Swaps [Member] | Investment Grade Risk Exposure [Member] | Credit [Member]
Derivative [Line Items]
Notional Amount	2,402	[1]	1,628	[1]
Fair Value	(7)		(34)
Weighted Average Years to Maturity	3 years		3 years
Underlying Referenced Credit Obligation Type	Corporate Credit/ Foreign Gov.	[3]	Corporate Credit/ Foreign Gov.	[3]
Average Credit Rating	A	[3]	A+	[3]
Offsetting Notional Amount	1,368	[2]	1,424	[2]
Offsetting Fair Value	(30)	[2]	(15)	[2]
Corporate Credit [Member] | Single Name Credit Default Swaps [Member] | Below Investment Grade Risk Exposure [Member] | Credit [Member]
Derivative [Line Items]
Notional Amount	144	[1]	170	[1]
Fair Value	(1)		(7)
Weighted Average Years to Maturity	1 year		2 years
Underlying Referenced Credit Obligation Type	Corporate Credit	[3]	Corporate Credit	[3]
Average Credit Rating	BB-	[3]	BB-	[3]
Offsetting Notional Amount	144	[2]	144	[2]
Offsetting Fair Value	(4)	[2]	(5)	[2]
Corporate Credit [Member] | Basket Credit Default Swaps [Member] | Investment Grade Risk Exposure [Member] | Credit [Member]
Derivative [Line Items]
Notional Amount	4,434	[1],[4]	3,645	[1],[4]
Fair Value	(10)	[4]	(92)	[4]
Weighted Average Years to Maturity	4 years	[4]	3 years	[4]
Underlying Referenced Credit Obligation Type	Corporate Credit	[3],[4]	Corporate Credit	[3],[4]
Average Credit Rating	BBB+	[3],[4]	BBB+	[3],[4]
Offsetting Notional Amount	2,677	[2],[4]	2,001	[2],[4]
Offsetting Fair Value	(4)	[2],[4]	29	[2],[4]
Corporate Credit [Member] | Basket Credit Default Swaps [Member] | Below Investment Grade Risk Exposure [Member] | Credit [Member]
Derivative [Line Items]
Notional Amount	353	[1],[4]	553	[1],[4]
Fair Value	(282)	[4]	(509)	[4]
Weighted Average Years to Maturity	3 years	[4]	3 years	[4]
Underlying Referenced Credit Obligation Type	Corporate Credit	[3],[4]	Corporate Credit	[3],[4]
Average Credit Rating	BB	[3],[4]	BBB+	[3],[4]
Offsetting Notional Amount	0	[2],[4]	0	[2],[4]
Offsetting Fair Value	0	[2],[4]	0	[2],[4]
Corporate Credit [Member] | Embedded Credit Derivatives [Member] | Investment Grade Risk Exposure [Member] | Credit [Member]
Derivative [Line Items]
Notional Amount	225	[1]	25	[1]
Fair Value	205		24
Weighted Average Years to Maturity	4 years		3 years
Underlying Referenced Credit Obligation Type	Corporate Credit	[3]	Corporate Credit	[3]
Average Credit Rating	BBB-	[3]	BBB-	[3]
Offsetting Notional Amount	0	[2]	0	[2]
Offsetting Fair Value	0	[2]	0	[2]
Corporate Credit [Member] | Embedded Credit Derivatives [Member] | Below Investment Grade Risk Exposure [Member] | Credit [Member]
Derivative [Line Items]
Notional Amount	300	[1]	500	[1]
Fair Value	264		411
Weighted Average Years to Maturity	4 years		5 years
Underlying Referenced Credit Obligation Type	Corporate Credit	[3]	Corporate Credit	[3]
Average Credit Rating	BB+	[3]	BB+	[3]
Offsetting Notional Amount	0	[2]	0	[2]
Offsetting Fair Value	0	[2]	0	[2]
CMBS Credit [Member] | Basket Credit Default Swaps [Member] | Investment Grade Risk Exposure [Member] | Credit [Member]
Derivative [Line Items]
Notional Amount	330	[1],[4]	525	[1],[4]
Fair Value	(24)	[4]	(98)	[4]
Weighted Average Years to Maturity	4 years	[4]	5 years	[4]
Underlying Referenced Credit Obligation Type	CMBS Credit	[3],[4]	CMBS Credit	[3],[4]
Average Credit Rating	A	[3],[4]	BBB+	[3],[4]
Offsetting Notional Amount	330	[2],[4]	525	[2],[4]
Offsetting Fair Value	24	[2],[4]	98	[2],[4]
CMBS Credit [Member] | Basket Credit Default Swaps [Member] | Below Investment Grade Risk Exposure [Member] | Credit [Member]
Derivative [Line Items]
Notional Amount	195	[1],[4]
Fair Value	(54)	[4]
Weighted Average Years to Maturity	4 years	[4]
Underlying Referenced Credit Obligation Type	CMBS Credit	[3],[4]
Average Credit Rating	B+	[3],[4]
Offsetting Notional Amount	195	[2],[4]
Offsetting Fair Value	$ 54	[2],[4]

[1] Notional amount is equal to the maximum potential future loss amount. There is no specific collateral related to these contracts or recourse provisions included in the contracts to offset losses.

[2] The Company has entered into offsetting credit default swaps to terminate certain existing credit default swaps, thereby offsetting the future changes in value of, or losses paid related to, the original swap.

[3] The average credit ratings are based on availability and the midpoint of the applicable ratings among Moody’s, S&P, and Fitch. If no rating is available from a rating agency, then an internally developed rating is used.

[4] Includes $5.0 billion and $4.2 billion as of September 30, 2012 and December 31, 2011, respectively, of standard market indices of diversified portfolios of corporate issuers referenced through credit default swaps. These swaps are subsequently valued based upon the observable standard market index. Also includes $353 and $533 as of September 30, 2012 and December 31, 2011, respectively, of customized diversified portfolios of corporate issuers referenced through credit default swaps.