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Collateralized Transactions (Financial instruments owned and pledged where the counterparty has the right to repledge) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Disclosure Collateralized Transactions [Abstract]
Stocks	$ 1,150	$ 1,574
U.S. and foreign government securities	54	359
Financial Instruments Owned and Pledged as Collateral - Eligible to be Repledged by Counterparty	$ 1,204	$ 1,933

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- References

No definition available.

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- Definition

Fair value of stocks held by the entity for its own account (proprietary securities) for trading or investment purposes that are carried at fair value and pledged to counterparties as collateral for financing transactions where counterparty has the right to re-pledge such.

+ References

No definition available.

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Balance Type:	debit
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- Definition

Fair value of U.S. and foreign government obligations held by the entity for its own account (proprietary securities) for trading or investment purposes that are carried at fair value and pledged to counterparties as collateral for financing transactions where counterparty has the right to re-pledge such.

+ References

No definition available.

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- Definition

Fair value of financial instrument held by the entity for its own account (proprietary securities) for trading or investment purposes that are carried at fair value and pledged to counterparties as collateral for financing transactions where counterparty has the right to re-pledge such.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66007379&loc=d3e113888-111728

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