Investments and Derivative Instruments (Details 19) (USD $) In Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2011	Dec. 31, 2010
Derivative [Line Items]
Notional Amount	$ 126,446	$ 136,854
Fair Value	(404)	(547)
Corporate Credit/Foreign Gov. [Member] | Single name credit default swaps [Member] | Investment grade risk exposure [Member] | Credit [Member]
Derivative [Line Items]
Notional Amount	1,586	1,562
Fair Value	(3)	(14)
Weighted Average Years to Maturity	3 years	3 years
Underlying Referenced Credit Obligation Type	Corporate Credit/ Foreign Gov.	Corporate Credit/ Foreign Gov.
Average Credit Rating	A+	A+
Offsetting Notional Amount	1,446	1,447
Offsetting Fair Value	(53)	(41)
Corporate Credit [Member] | Single name credit default swaps [Member] | Below investment grade risk exposure [Member] | Credit [Member]
Derivative [Line Items]
Notional Amount	180	204
Fair Value	(4)	(6)
Weighted Average Years to Maturity	2 years	3 years
Underlying Referenced Credit Obligation Type	Corporate Credit	Corporate Credit
Average Credit Rating	BB-	BB-
Offsetting Notional Amount	144	168
Offsetting Fair Value	(8)	(13)
Corporate Credit [Member] | Basket credit default swaps [Member] | Investment grade risk exposure [Member] | Credit [Member]
Derivative [Line Items]
Notional Amount	3,144	3,145
Fair Value	10	(1)
Weighted Average Years to Maturity	3 years	4 years
Underlying Referenced Credit Obligation Type	Corporate Credit	Corporate Credit
Average Credit Rating	BBB+	BBB+
Offsetting Notional Amount	2,128	2,019
Offsetting Fair Value	(18)	(14)
Corporate Credit [Member] | Basket credit default swaps [Member] | Below investment grade risk exposure [Member] | Credit [Member]
Derivative [Line Items]
Notional Amount	578	767
Fair Value	(396)	(381)
Weighted Average Years to Maturity	4 years	4 years
Underlying Referenced Credit Obligation Type	Corporate Credit	Corporate Credit
Average Credit Rating	BBB+	BBB+
Offsetting Notional Amount	25	25
Offsetting Fair Value	1
Corporate Credit [Member] | Embedded credit derivatives [Member] | Investment grade risk exposure [Member] | Credit [Member]
Derivative [Line Items]
Notional Amount	25	25
Fair Value	24	25
Weighted Average Years to Maturity	3 years	4 years
Underlying Referenced Credit Obligation Type	Corporate Credit	Corporate Credit
Average Credit Rating	BBB-	BBB-
Offsetting Notional Amount	0	0
Offsetting Fair Value	0	0
Corporate Credit [Member] | Embedded credit derivatives [Member] | Below investment grade risk exposure [Member] | Credit [Member]
Derivative [Line Items]
Notional Amount	500	525
Fair Value	438	463
Weighted Average Years to Maturity	6 years	6 years
Underlying Referenced Credit Obligation Type	Corporate Credit	Corporate Credit
Average Credit Rating	BB+	BB+
Offsetting Notional Amount	0	0
Offsetting Fair Value	0	0
CMBS Credit [Member] | Basket credit default swaps [Member] | Investment grade risk exposure [Member] | Credit [Member]
Derivative [Line Items]
Notional Amount	525	525
Fair Value	(66)	(50)
Weighted Average Years to Maturity	6 years	6 years
Underlying Referenced Credit Obligation Type	CMBS Credit	CMBS Credit
Average Credit Rating	BBB+	BBB+
Offsetting Notional Amount	525	525
Offsetting Fair Value	66	50
Basket credit default swaps [Member] | Below investment grade risk exposure [Member] | Credit [Member]
Derivative [Line Items]
Offsetting Fair Value		0
Credit [Member]
Derivative [Line Items]
Notional Amount	6,537	6,753
Fair Value	3	36
Offsetting Notional Amount	4,268	4,184
Offsetting Fair Value	$ (12)	$ (18)