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Financial Instruments Owned And Financial Instruments Sold, But Not Yet Purchased (Components Of Trading Securities Owned And Trading Securities Sold, But Not Yet Purchased) (Details) - USD ($) $ in Thousands | Sep. 30, 2018 | Dec. 31, 2017
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Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |
Financial instruments owned, at fair value | $ 1,162,732 | $ 1,143,684
U.S. Government Agency Securities [Member] |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |
Financial instruments owned, at fair value | 167,886 | 147,223
Corporate Fixed Income Securities [Member] |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |
Financial instruments owned, at fair value | 290,627 | 325,471
Corporate Equity Securities [Member] |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |
Financial instruments owned, at fair value | 69,205 | 46,802
State and Municipal Securities [Member] |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |
Financial instruments owned, at fair value | 149,207 | 169,699
U.S. Government Securities [Member] |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |
Financial instruments owned, at fair value | 36,214 | 13,466
Sovereign Debt [Member] |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |
Financial instruments owned, at fair value | 15,996 | 32,470
Securities Sold, But Not yet Purchased [Member] |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |
Financial instruments owned, at fair value | 911,374 | 778,863
Securities Sold, But Not yet Purchased [Member] | U.S. Government Agency Securities [Member] |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |
Trading securities owned |  | 10,348
Securities Sold, But Not yet Purchased [Member] | Corporate Fixed Income Securities [Member] |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |
Fixed income securities | 213,335 | 180,755
Securities Sold, But Not yet Purchased [Member] | Corporate Equity Securities [Member] |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |
Equity securities | 78,895 | 38,510
Securities Sold, But Not yet Purchased [Member] | U.S. Government Securities [Member] |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |
Trading securities owned | 512,275 | 442,402
Securities Sold, But Not yet Purchased [Member] | Mortgage Backed Securities [Member] | Agency [Member] |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |
Trading securities owned | 95,312 | 86,612
Securities Sold, But Not yet Purchased [Member] | Sovereign Debt [Member] |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |
Sovereign debt | 11,557 | 20,236
Securities Owned |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |
Asset-backed securities | 29,806 | 76,752
Financial instruments owned, at fair value | 1,162,732 | 1,143,684
Securities Owned | U.S. Government Agency Securities [Member] |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |
Trading securities owned | 167,886 | 147,223
Securities Owned | Corporate Fixed Income Securities [Member] |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |
Fixed income securities | 290,627 | 325,471
Securities Owned | Corporate Equity Securities [Member] |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |
Equity securities | 69,205 | 46,802
Securities Owned | State and Municipal Securities [Member] |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |
State and municipal securities | 149,207 | 169,699
Securities Owned | U.S. Government Securities [Member] |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |
Trading securities owned | 36,214 | 13,466
Securities Owned | Mortgage Backed Securities [Member] | Agency [Member] |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |
Trading securities owned | 380,044 | 302,445
Securities Owned | Mortgage Backed Securities [Member] | Non-Agency [Member] |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |
Trading securities owned | 23,747 | 29,356
Securities Owned | Sovereign Debt [Member] |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |
Sovereign debt | $ 15,996 | $ 32,470

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- Definition Investments in notes or bonds that are collateralized by a specific group of underlying assets owned by the issuer of the notes or bonds which are short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three-years ago does not become a cash equivalent when its remaining maturity is three months. + References No definition available. + Details
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- Definition The fair value as of the balance sheet date of firm holdings in fixed income obligations issued by foreign governments. Includes both pledged (to counterparties as collateral for financing transactions) and unpledged holdings. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 940 -SubTopic 320 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=35711157&loc=d3e42546-110969 + Details
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- Definition Fair value of obligations arising from corporate debt obligations sold short. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 940 -SubTopic 320 -Section 35 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=35711043&loc=d3e42429-110968 + Details
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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. + Details
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- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading) and investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.4) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 + Details
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- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109979856&loc=d3e26610-111562 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=109979856&loc=d3e26610-111562 + Details
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