Commitments, Contingencies, And Guarantees (Narrative) (Detail) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Financial Instruments Owned and Pledged as Collateral [Line Items]
Securities lending collateral	$ 1,140	$ 1,046
Carrying value of limited partnerships and partially-owned investment companies included in other investments	3,300
Funding commitments relating to limited partnerships and partially-owned investment companies	2,000
Unrecognized tax benefits	17
Derivative liability subject to a master netting agreement	9	$ 1
Purchase Commitment, Remaining Minimum Amount Committed	788
Overnight and Continuous [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Secured Borrowings, Gross, Difference, Amount	(1)
Cash and Cash Equivalents [Member] \| Overnight and Continuous [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Securities lending collateral	449
U.S. Treasury And Agency [Member] \| Overnight and Continuous [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Securities lending collateral	53
Corporate [Member] \| Overnight and Continuous [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Securities lending collateral	4
Equity Option [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Derivative Asset, Fair Value, Gross Liability	$ 0

Carrying value of limited partnerships and partially-owned investment companies included in other investments.

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- Definition

Funding commitments relating to limited partnerships and partially-owned investment companies included in other investments.

+ References

No definition available.

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- Definition

Fair value of liability associated with financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=51825145&loc=SL20226003-175313

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-Publisher FASB
-Name Accounting Standards Codification
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-Paragraph 4B
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Fair value, after effects of master netting arrangements, of financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset offset against the right to receive collateral. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
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- Definition

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.

+ References

No definition available.

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- Definition

Minimum amount to be expended to satisfy the terms of arrangements in which the entity has agreed to expend funds to procure goods or services, excluding long-term purchase commitments or unconditional purchase obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(19))
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- Definition

Amount of secured borrowings in excess of (less than) the liability for repurchase agreements and securities lending transactions, before offset, included in offsetting disclosures.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
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- Definition

The carrying amount (fair value) as of the balance sheet date of securities held that had been pledged by counterparties under financing and lending arrangements, pursuant to which the entity has the right by agreement or custom to sell or re-pledge such securities.

+ References

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

Amount of unrecognized tax benefits.

+ References

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