Fair Value Measurements (Fair Value And Maximum Future Funding Commitments Related To Investments) (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2016	Dec. 31, 2015
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Maximum future funding commitments	$ 2,112	$ 824
Fair Value	3,658	2,477
Financial [Member]
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Maximum future funding commitments	210	105
Fair Value	580	300
Real Assets [Member]
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Maximum future funding commitments	321	140
Fair Value	577	474
Distressed [Member]
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Maximum future funding commitments	217	218
Fair Value	451	261
Private Credit [Member]
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Maximum future funding commitments	349	209
Fair Value	272	265
Traditional [Member]
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Maximum future funding commitments	1,001	152
Fair Value	1,498	895
Vintage [Member]
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Maximum future funding commitments	14
Fair Value	36	13
Investment Funds [Member]
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Fair Value	$ 244	$ 269
Minimum [Member]
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Notice Period For Redemption For Alternative Investments Investment Funds	5 days
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]
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Notice Period For Redemption For Alternative Investments Investment Funds	120 days
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

Notice period in days for redemption of investment funds alternative investments (employ various investment strategies such as long/short equity and arbitrage/distressed.)

+ References

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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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