Derivative Financial Instruments - Gain (Loss) Recognized (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Derivative instruments not designated as hedging instruments \| Trading revenues, net
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized	$ (2,473)	$ 28,790
Derivative instruments not designated as hedging instruments \| Foreign currency, Futures contracts \| Trading revenues, net
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized	2,712	312
Derivative instruments not designated as hedging instruments \| Equity, Futures contracts \| Trading revenues, net
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized	(7,998)	8,922
Derivative instruments not designated as hedging instruments \| Equity, Swap contracts \| Trading revenues, net
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized	(795)	1,886
Derivative instruments not designated as hedging instruments \| Equity, Listed options \| Trading revenues, net
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized	(24)	3,871
Derivative instruments not designated as hedging instruments \| Fixed income, Futures contracts \| Trading revenues, net
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized	(118)	6,833
Derivative instruments not designated as hedging instruments \| Commodity, Futures contracts \| Trading revenues, net
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized	3,750	6,966
Derivative instruments designated as hedging instruments \| Foreign currency, Forward contracts \| Accumulated other comprehensive (loss) income
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized	$ (389)	$ (149)

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- Definition

The effective portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments that was recognized in other comprehensive income during the current period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624171-113959

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- Definition

Amount of realized and unrealized gain (loss) of derivative instruments not designated or qualifying as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624171-113959

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