Investments and Derivative Instruments (Details 19) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Dec. 31, 2012
Derivative [Line Items]
Notional Amount	$ 181,764				$ 205,854
Fair Value	(1,746)				(1,448)
Credit [Member]
Derivative [Line Items]
Notional Amount	3,837	[1]			4,652	[1]
Fair Value	132				275
Offsetting Notional Amount	2,081	[2]			2,671	[2]
Offsetting Fair Value	18	[2]			11	[2]
Corporate Credit/Foreign Gov. [Member] | Single Name Credit Default Swaps [Member] | Investment Grade Risk Exposure [Member] | Credit [Member]
Derivative [Line Items]
Notional Amount	1,461	[1]			1,787	[1]
Fair Value	9				8
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	789	[2]			878	[2]
Offsetting Fair Value	(11)	[2]			(19)	[2]
Corporate Credit [Member] | Single Name Credit Default Swaps [Member] | Below Investment Grade Risk Exposure [Member] | Credit [Member]
Derivative [Line Items]
Notional Amount	67	[1]			114	[1]
Fair Value	0				(1)
Weighted Average Years to Maturity	1 year		1 year
Underlying Referenced Credit Obligation Type	Corporate Credit	[3]	Corporate Credit	[3]
Average Credit Rating	B-	[3]	B+	[3]
Offsetting Notional Amount	67	[2]			114	[2]
Offsetting Fair Value	(1)	[2]			(3)	[2]
Corporate Credit [Member] | Basket Credit Default Swaps [Member] | Investment Grade Risk Exposure [Member] | Credit [Member]
Derivative [Line Items]
Notional Amount	1,718	[1]			2,074	[1]
Fair Value	10				11
Weighted Average Years to Maturity	2 years		2 years
Underlying Referenced Credit Obligation Type	Corporate Credit	[3]	Corporate Credit	[3]
Average Credit Rating	BBB+	[3]	BBB+	[3]
Offsetting Notional Amount	872	[2]			1,326	[2]
Offsetting Fair Value	(6)	[2]			(6)	[2]
Corporate Credit [Member] | Basket Credit Default Swaps [Member] | Below Investment Grade Risk Exposure [Member] | Credit [Member]
Derivative [Line Items]
Notional Amount	88	[1]			115	[1]
Fair Value	7				(27)
Weighted Average Years to Maturity	5 years		4 years
Underlying Referenced Credit Obligation Type	Corporate Credit	[3]	CMBS Credit	[3]
Average Credit Rating	BB+	[3]	B+	[3]
Offsetting Notional Amount	0	[2]			115	[2]
Offsetting Fair Value	0	[2]			27	[2]
Corporate Credit [Member] | Embedded Credit Derivatives [Member] | Investment Grade Risk Exposure [Member] | Credit [Member]
Derivative [Line Items]
Notional Amount	150	[1]			325	[1]
Fair Value	142				296
Weighted Average Years to Maturity	4 years		4 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]
CMBS Credit [Member] | Basket Credit Default Swaps [Member] | Investment Grade Risk Exposure [Member] | Credit [Member]
Derivative [Line Items]
Notional Amount	238	[1]			237	[1]
Fair Value	(12)				(12)
Weighted Average Years to Maturity	4 years		4 years
Underlying Referenced Credit Obligation Type	CMBS Credit	[3]	CMBS Credit	[3]
Average Credit Rating	A	[3]	A	[3]
Offsetting Notional Amount	238	[2]			238	[2]
Offsetting Fair Value	12	[2]			12	[2]
CMBS Credit [Member] | Basket Credit Default Swaps [Member] | Below Investment Grade Risk Exposure [Member] | Credit [Member]
Derivative [Line Items]
Notional Amount	115	[1]
Fair Value	(24)
Weighted Average Years to Maturity	4 years
Underlying Referenced Credit Obligation Type	CMBS Credit	[3]
Average Credit Rating	B	[3]
Offsetting Notional Amount	115	[2]
Offsetting Fair Value	$ 24	[2]

[1]

[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.