Loans To And Investments In Associated Companies (FXCM) (Narrative) (Details)	Dec. 31, 2016	Sep. 01, 2016
Investment in FXCM [Member]
Investments in and Advances to Affiliates [Line Items]
Percentage of ownership owned	49.90%	49.90%

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66011266&loc=d3e33918-111571

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant