Collateralized Transactions (Collateral Received) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Collateralized Transactions
Collateral with rights to sell or repledge	$ 597,886	$ 599,244
Collateral that was sold or repledged	$ 471,985	$ 475,113

The sum of the fair values, as of the date of each statement of financial position presented, of assets which are owned but transferred to serve as collateral for the payment of debt obligations, primarily secured borrowings, repurchase agreements or other current or potential obligations, and that are reclassified and separately reported in the statement of financial position because the transferee has the right by contract or custom to sell or re-pledge them.

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

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