Collateralized Transactions - Assets Loaned or Pledged (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Collateralized Agreements [Abstract]
Trading assets	$ 39,625	$ 39,430

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 does not have the right to re-pledge such.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
-Subparagraph (b)(1)(i)
-URI http://asc.fasb.org/extlink&oid=109249958&loc=SL6224234-111729

Name:	us-gaap_FinancialInstrumentsOwnedAndPledgedAsCollateralAmountNotEligibleToBeRepledgedByCounterparty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant