Investments and Derivative Instruments (Details 19) (USD $) In Millions	9 Months Ended	12 Months Ended
Sep. 30, 2011	Dec. 31, 2010
Derivative [Line Items]
Notional Amount	$ 134,480	$ 136,854
Fair Value	(164)	(547)
Corporate Credit/Foreign Gov. [Member] \| Single Name Credit Default Swaps [Member] \| Investment Grade Risk Exposure [Member] \| Credit [Member]
Derivative [Line Items]
Notional Amount	1,569	1,562
Fair Value	(42)	(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	(10)	(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	(10)	(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	(3)	(13)
Corporate Credit [Member] \| Basket Credit Default Swaps [Member] \| Investment Grade Risk Exposure [Member] \| Credit [Member]
Derivative [Line Items]
Notional Amount	3,162	3,145
Fair Value	(118)	(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	2,044	2,019
Offsetting Fair Value	45	(14)
Corporate Credit [Member] \| Basket Credit Default Swaps [Member] \| Below Investment Grade Risk Exposure [Member] \| Credit [Member]
Derivative [Line Items]
Notional Amount	553	767
Fair Value	(481)	(381)
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	25
Offsetting Fair Value	0
Corporate Credit [Member] \| Embedded Credit Derivatives [Member] \| Investment Grade Risk Exposure [Member] \| Credit [Member]
Derivative [Line Items]
Notional Amount	25	25
Fair Value	23	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	400	463
Weighted Average Years to Maturity	5 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	(133)	(50)
Weighted Average Years to Maturity	5 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	133	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	6,514	6,753
Fair Value	(361)	36
Offsetting Notional Amount	4,159	4,184
Offsetting Fair Value	$ 165	$ (18)

Average credit rating.

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- Definition

Offsetting Notional Amount.

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Balance Type:	credit
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- Definition

Underlying referenced credit obligation type.

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- Definition

Monetary amount specified by the derivative(s). Expressed as an absolute value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 12

+ Details

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- Definition

The average time remaining until maturity on the group of derivatives identified.

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- Definition

The net amount as of the balance sheet date of the fair value of derivative assets and derivative liabilities that in accordance with the entity's accounting policy were offset against collateral under a master netting arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FIN39-1

-Paragraph 10B

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 8

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6935481&loc=d3e41678-113959

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- Definition

Fair value as of the balance sheet date of the assets less the liabilities of a derivative or group of derivatives.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 15

-URI http://asc.fasb.org/extlink&oid=6947722&loc=d3e13495-108611

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 45

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 45

-Paragraph 6

-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41271-113958

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 10

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6947722&loc=d3e13433-108611

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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