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Derivative Financial Instruments (Statement Of Operations Information) (Details) - Not Designated as Hedging Instruments [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Derivative [Line Items]
Derivative financial instruments, net gain (loss) recognized	$ 1,539	$ 1,554	$ 5,043	$ 5,369
Revenues - principal transactions and other income [Member] | Foreign currency forward contracts [Member]
Derivative [Line Items]
Derivative financial instruments, net gain (loss) recognized	14	(34)	65	(132)
Revenues - net trading [Member] | Other Extended Settlement Trades [Member]
Derivative [Line Items]
Derivative financial instruments, net gain (loss) recognized	(10)	4	(10)	(15)
Revenues - net trading [Member] | TBAs and Other Forward Agency MBS[Member]
Derivative [Line Items]
Derivative financial instruments, net gain (loss) recognized	$ 1,535	$ 1,584	$ 4,988	$ 5,516

X

- Definition

Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5618551-113959

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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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