Fair Value Measurements (Fair Value And Maximum Future Funding Commitments Related To Investments) (Detail) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2015	Dec. 31, 2014
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Maximum future funding commitments	$ 916	$ 1,010
Fair Value	2,504	2,561
Financial [Member]
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Maximum future funding commitments	107	145
Fair Value	309	282
Real Assets [Member]
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Maximum future funding commitments	168	210
Fair Value	473	451
Distressed [Member]
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Maximum future funding commitments	231	175
Fair Value	265	232
Private Credit [Member]
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Maximum future funding commitments	226	190
Fair Value	272	299
Traditional [Member]
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Maximum future funding commitments	184	289
Fair Value	885	908
Vintage [Member]
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Maximum future funding commitments	0	1
Fair Value	14	11
Investment Funds [Member]
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Maximum future funding commitments	0	0
Fair Value	$ 286	$ 378
Minimum [Member] \| Financial [Member]
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Expected liquidation period of underlying assets	5 years	5 years
Minimum [Member] \| Real Assets [Member]
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Expected liquidation period of underlying assets	3 years	3 years
Minimum [Member] \| Distressed [Member]
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Expected liquidation period of underlying assets	5 years	5 years
Minimum [Member] \| Private Credit [Member]
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Expected liquidation period of underlying assets	3 years	3 years
Minimum [Member] \| Traditional [Member]
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Expected liquidation period of underlying assets	3 years	3 years
Minimum [Member] \| Vintage [Member]
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Expected liquidation period of underlying assets	1 year	1 year
Maximum [Member] \| Financial [Member]
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Expected liquidation period of underlying assets	9 years	9 years
Maximum [Member] \| Real Assets [Member]
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Expected liquidation period of underlying assets	7 years	7 years
Maximum [Member] \| Distressed [Member]
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Expected liquidation period of underlying assets	9 years	9 years
Maximum [Member] \| Private Credit [Member]
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Expected liquidation period of underlying assets	7 years	7 years
Maximum [Member] \| Traditional [Member]
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Expected liquidation period of underlying assets	9 years	9 years
Maximum [Member] \| Vintage [Member]
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Expected liquidation period of underlying assets	2 years	2 years

Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]

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- Definition

Fair value of investments in certain entities that calculate net asset value per share, including, but not limited to, by unit, membership interest, or other ownership interest. Investments include, but are not limited to, investments in certain hedge funds, venture capital funds, private equity funds, real estate partnerships or funds.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 6A

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=36462937&loc=SL6742756-110258

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- Definition

Estimate remaining period the underlying assets are expected to be liquidated by the investees for investments for which net asset value per share is calculated (including by unit, membership interest, or other ownership interest unit measure), in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 6A

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=36462937&loc=SL6742756-110258

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- Definition

The amount of unfunded commitments for which the entity is obligated, to those certain investments for which net asset value per share is calculated (including by unit, membership interest, or other equity (ownership interest) unit measure) (alternative investments).

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 6A

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=36462937&loc=SL6742756-110258

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