Receivables From And Payables To Brokers, Dealers And Clearing Organizations (Amounts Payable To Brokers, Dealers, And Clearing Organizations) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Due To And From Broker Dealers And Clearing Organizations [Abstract]
Deposits received from securities loaned	$ 691,150	$ 219,782
Payable to clearing organizations	201,510	27,223
Securities failed to receive	35,472	29,297
Payables to broker, dealers and clearing organizations, Total	$ 928,132	$ 276,302

Amount payable to broker-dealers or clearing organizations for executing or clearing trades or orders.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 940
-SubTopic 20
-Section 25
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=68072869&loc=d3e41256-110953

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- Definition

The amount of cash received as security in return for loaning securities to another party.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-04(11))
-URI http://asc.fasb.org/extlink&oid=6488278&loc=d3e603758-122996

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- References

No definition available.

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- Definition

Amount payable to broker-dealers and clearing organizations, including, but not limited to, securities failed-to-receive, certain deposits received for securities loaned, open transactions, and floor-brokerage payables.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 940
-SubTopic 20
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=35710130&loc=d3e41645-110958

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- Definition

Amount payable as the result of fail-to-receive. A fail-to-receive is a securities purchase from another broker-dealer not received from the selling broker-dealer by the close of business on the settlement date.

+ References

No definition available.

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