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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, 2024 | Dec. 31, 2023
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Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |  |
Financial instruments owned, at fair value |  | $ 1,351,298 | $ 918,741
U.S. Government Agency Securities [Member] |  |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |  |
Financial instruments owned, at fair value |  | 198,038 | 106,634
Corporate Fixed Income Securities [Member] |  |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |  |
Financial instruments owned, at fair value |  | 302,247 | 237,671
Corporate Equity Securities [Member] |  |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |  |
Financial instruments owned, at fair value |  | 58,526 | 52,520
State and Municipal Securities [Member] |  |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |  |
Financial instruments owned, at fair value |  | 244,491 | 223,155
U.S. Government Securities [Member] |  |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |  |
Financial instruments owned, at fair value |  | 19,662 | 32,411
Securities Sold, But Not yet Purchased [Member] |  |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |  |
Other | [1] | 1,052 | 11,489
Financial instruments owned, at fair value |  | 768,909 | 497,741
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 |  | 186,964 | 138,359
Securities Sold, But Not yet Purchased [Member] | Corporate Equity Securities [Member] |  |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |  |
Financial instruments owned, at fair value |  | 24,221 | 21,576
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 |  | 441,703 | 273,653
Securities Sold, But Not yet Purchased [Member] | Mortgage-Backed Securities [Member] | Agency Securities [Member] |  |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |  |
Trading securities owned |  | 114,969 | 52,664
Securities Owned [Member] |  |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |  |
Asset-backed securities |  | 96,290 | 19,604
Other | [2] | 62,531 | 86,843
Financial instruments owned, at fair value |  | 1,351,298 | 918,741
Securities Owned [Member] | U.S. Government Agency Securities [Member] |  |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |  |
Trading securities owned |  | 198,038 | 106,634
Securities Owned [Member] | Corporate Fixed Income Securities [Member] |  |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |  |
Fixed income securities |  | 302,247 | 237,671
Securities Owned [Member] | Corporate Equity Securities [Member] |  |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |  |
Financial instruments owned, at fair value |  | 58,526 | 52,520
Securities Owned [Member] | State and Municipal Securities [Member] |  |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |  |
State and municipal securities |  | 244,491 | 223,155
Securities Owned [Member] | U.S. Government Securities [Member] |  |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |  |
Trading securities owned |  | 19,662 | 32,411
Securities Owned [Member] | Mortgage-Backed Securities [Member] | Agency Securities [Member] |  |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |  |
Trading securities owned |  | $ 369,513 | $ 159,903
[1] | Includes syndicated loans, U.S. government agency securities, sovereign debt, state and municipal securities, and asset-backed securities.
[2] | Includes syndicated loans, non-agency mortgage-backed securities, and sovereign debt.

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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 Fair value of firm holdings in securities classified as other. Includes pledged and unpledged holdings. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 940 -SubTopic 320 -Name Accounting Standards Codification -Section 45 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479035/940-320-45-2 + 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 Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 6B -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-6B + Details
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