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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, 2023 | Dec. 31, 2022
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Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |  |
Financial instruments owned, at fair value |  | $ 1,056,745 | $ 731,752
U.S. Government Agency Securities [Member] |  |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |  |
Financial instruments owned, at fair value |  | 158,086 | 73,608
Corporate Fixed Income Securities [Member] |  |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |  |
Financial instruments owned, at fair value |  | 321,842 | 202,169
Corporate Equity Securities [Member] |  |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |  |
Financial instruments owned, at fair value |  | 43,091 | 38,129
State and Municipal Securities [Member] |  |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |  |
Financial instruments owned, at fair value |  | 163,139 | 126,237
U.S. Government Securities [Member] |  |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |  |
Financial instruments owned, at fair value |  | 10,479 | 38,956
Securities Sold, But Not yet Purchased [Member] |  |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |  |
Other | [1] | 12,683 | 5,817
Financial instruments owned, at fair value |  | 578,290 | 454,817
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 |  | 5,439 | 3,971
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 |  | 135,080 | 134,381
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 |  | 20,114 | 11,590
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 |  | 334,630 | 254,265
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 |  | 70,344 | 44,793
Securities Owned [Member] |  |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |  |
Asset-backed securities |  | 63,046 | 8,270
Other | [2] | 97,768 | 71,741
Financial instruments owned, at fair value |  | 1,056,745 | 731,752
Securities Owned [Member] | U.S. Government Agency Securities [Member] |  |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |  |
Trading securities owned |  | 158,086 | 73,608
Securities Owned [Member] | Corporate Fixed Income Securities [Member] |  |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |  |
Fixed income securities |  | 321,842 | 202,169
Securities Owned [Member] | Corporate Equity Securities [Member] |  |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |  |
Financial instruments owned, at fair value |  | 43,091 | 38,129
Securities Owned [Member] | State and Municipal Securities [Member] |  |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |  |
State and municipal securities |  | 163,139 | 126,237
Securities Owned [Member] | U.S. Government Securities [Member] |  |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |  |
Trading securities owned |  | 10,479 | 38,956
Securities Owned [Member] | Mortgage-Backed Securities [Member] | Agency Securities [Member] |  |  |
Schedule Of Trading Securities And Other Trading Assets [Line Items] |  |  |
Trading securities owned |  | $ 199,294 | $ 172,642
[1] | Includes asset-backed securities, syndicated loans, and state and municipal 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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