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Fair Value Of Financial Instruments (Fair Value of Assets and Liabilities Measured on Recurring Basis) (Details) - USD ($) $ in Thousands | Jun. 30, 2025 | Dec. 31, 2024
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Financial instruments owned |  | $ 1,343,513 |  | $ 1,169,008 |
Available-for-sale securities |  | 1,546,392 |  | 1,584,598 |
Financial instruments sold, but not yet purchased, at fair value |  | 819,555 |  | 646,271 |
U.S. Government Agency Securities [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Available-for-sale securities |  | 2,338 |  |  |
Corporate Fixed Income Securities [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Available-for-sale securities |  | 434,137 |  |  |
State and Municipal Securities [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Available-for-sale securities |  | 2,350 |  |  |
Agency Mortgage-Backed Securities [Member] | Agency Securities [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Available-for-sale securities |  | 948,159 |  | 921,563 |
Agency Mortgage-Backed Securities [Member] | Commercial [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Available-for-sale securities |  | 41,656 |  | 67,956 |
Agency Mortgage-Backed Securities [Member] | Non-Agency [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Available-for-sale securities |  | 168 |  | 199 |
Fair Value, Recurring [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Available-for-sale securities |  | 1,546,392 |  | 1,584,598 |
Investments |  | 78,572 |  | 75,358 |
Derivative contracts, Assets |  | 82,341 | [1] | 110,814 | [2]
Cash equivalents measured at NAV |  | 5,061 |  | 1,932 |
Total Assets |  | 3,055,879 |  | 2,941,710 |
Financial instruments sold, but not yet purchased, at fair value |  | 819,555 |  | 646,271 |
Derivative contracts, Liabilities |  | 82,353 | [3] | 110,825 | [4]
Total Liabilities |  | 901,908 |  | 757,096 |
Fair Value, Recurring [Member] | U.S. Government Agency Securities [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Financial instruments owned |  | 122,226 |  | 149,479 |
Available-for-sale securities |  | 2,338 |  | 2,266 |
Fair Value, Recurring [Member] | Asset-Backed Securities [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Financial instruments owned |  | 113,938 |  | 113,033 |
Available-for-sale securities |  | 117,584 |  | 126,273 |
Fair Value, Recurring [Member] | Corporate Fixed Income Securities [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Financial instruments owned |  | 285,451 |  | 274,207 |
Available-for-sale securities |  | 434,137 |  | 463,992 |
Financial instruments sold, but not yet purchased, at fair value |  | 137,127 |  | 174,425 |
Fair Value, Recurring [Member] | Corporate Equity Securities [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Financial instruments owned |  | 59,147 |  | 50,787 |
Investments |  | 31,953 |  | 30,227 |
Financial instruments sold, but not yet purchased, at fair value |  | 31,361 |  | 34,437 |
Fair Value, Recurring [Member] | State and Municipal Securities [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Financial instruments owned |  | 213,226 |  | 229,342 |
Available-for-sale securities |  | 2,350 |  | 2,349 |
Fair Value, Recurring [Member] | Auction Rate Securities [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Investments |  | 554 |  | 558 |
Fair Value, Recurring [Member] | Other Investment [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Investments |  | 13,641 | [5] | 14,378 | [6]
Fair Value, Recurring [Member] | Investments in Funds and Partnerships Measured at NAV [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Investments |  | 32,424 |  | 30,195 |
Fair Value, Recurring [Member] | Assets At Fair Value On Recurring Basis Before Cash Equivalents Measured at NAV [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Total Assets |  | 3,050,818 |  | 2,939,778 |
Fair Value, Recurring [Member] | U.S. Government Securities [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Financial instruments owned |  | 24,466 |  | 20,045 |
Financial instruments sold, but not yet purchased, at fair value |  | 477,514 |  | 370,373 |
Fair Value, Recurring [Member] | Agency Mortgage-Backed Securities [Member] | Agency Securities [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Financial instruments owned |  | 476,953 |  | 262,629 |
Available-for-sale securities |  | 948,159 |  | 921,563 |
Financial instruments sold, but not yet purchased, at fair value |  | 171,839 |  | 65,946 |
Fair Value, Recurring [Member] | Agency Mortgage-Backed Securities [Member] | Commercial [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Available-for-sale securities |  | 41,656 |  | 67,956 |
Fair Value, Recurring [Member] | Agency Mortgage-Backed Securities [Member] | Non-Agency [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Available-for-sale securities |  | 168 |  | 199 |
Sovereign Debt [Member] | Fair Value, Recurring [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Financial instruments owned |  | 1,343,513 |  | 1,169,008 |
Other [Member] | Fair Value, Recurring [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Financial instruments owned |  | 48,106 | [7] | 69,486 | [8]
Financial instruments sold, but not yet purchased, at fair value |  | 1,714 | [9] | 1,090 | [10]
Level 1 [Member] | Fair Value, Recurring [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Investments |  | 14,879 |  | 14,691 |
Derivative contracts, Assets | [1] | 0 |  |  |
Total Assets |  | 98,505 |  | 85,715 |
Financial instruments sold, but not yet purchased, at fair value |  | 508,875 |  | 404,810 |
Total Liabilities |  | 508,875 |  | 404,810 |
Level 1 [Member] | Fair Value, Recurring [Member] | Corporate Fixed Income Securities [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Financial instruments owned |  | 33 |  | 507 |
Level 1 [Member] | Fair Value, Recurring [Member] | Corporate Equity Securities [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Financial instruments owned |  | 59,127 |  | 50,472 |
Investments |  | 14,878 |  | 14,661 |
Financial instruments sold, but not yet purchased, at fair value |  | 31,361 |  | 34,437 |
Level 1 [Member] | Fair Value, Recurring [Member] | Other Investment [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Investments |  | 1 | [5] | 30 | [6]
Level 1 [Member] | Fair Value, Recurring [Member] | U.S. Government Securities [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Financial instruments owned |  | 24,466 |  | 20,045 |
Financial instruments sold, but not yet purchased, at fair value |  | 477,514 |  | 370,373 |
Level 1 [Member] | Sovereign Debt [Member] | Fair Value, Recurring [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Financial instruments owned |  | 83,626 |  | 71,024 |
Level 2 [Member] | Fair Value, Recurring [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Available-for-sale securities |  | 1,546,392 |  | 1,584,598 |
Investments |  | 1 |  | 1 |
Derivative contracts, Assets |  | 82,341 | [1] | 110,814 | [2]
Total Assets |  | 2,847,777 |  | 2,733,896 |
Financial instruments sold, but not yet purchased, at fair value |  | 309,439 |  | 240,371 |
Derivative contracts, Liabilities |  | 82,353 | [3] | 110,825 | [4]
Total Liabilities |  | 391,792 |  | 351,196 |
Level 2 [Member] | Fair Value, Recurring [Member] | U.S. Government Agency Securities [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Financial instruments owned |  | 122,226 |  | 149,479 |
Available-for-sale securities |  | 2,338 |  | 2,266 |
Level 2 [Member] | Fair Value, Recurring [Member] | Asset-Backed Securities [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Financial instruments owned |  | 112,904 |  | 111,999 |
Available-for-sale securities |  | 117,584 |  | 126,273 |
Level 2 [Member] | Fair Value, Recurring [Member] | Corporate Fixed Income Securities [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Financial instruments owned |  | 285,418 |  | 273,700 |
Available-for-sale securities |  | 434,137 |  | 463,992 |
Financial instruments sold, but not yet purchased, at fair value |  | 137,127 |  | 174,425 |
Level 2 [Member] | Fair Value, Recurring [Member] | Corporate Equity Securities [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Financial instruments owned |  | 20 |  | 315 |
Investments |  | 1 |  | 1 |
Level 2 [Member] | Fair Value, Recurring [Member] | State and Municipal Securities [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Financial instruments owned |  | 213,226 |  | 229,342 |
Available-for-sale securities |  | 2,350 |  | 2,349 |
Level 2 [Member] | Fair Value, Recurring [Member] | Agency Mortgage-Backed Securities [Member] | Agency Securities [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Financial instruments owned |  | 476,953 |  | 262,629 |
Available-for-sale securities |  | 948,159 |  | 921,563 |
Financial instruments sold, but not yet purchased, at fair value |  | 171,839 |  | 65,946 |
Level 2 [Member] | Fair Value, Recurring [Member] | Agency Mortgage-Backed Securities [Member] | Commercial [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Available-for-sale securities |  | 41,656 |  | 67,956 |
Level 2 [Member] | Fair Value, Recurring [Member] | Agency Mortgage-Backed Securities [Member] | Non-Agency [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Available-for-sale securities |  | 168 |  | 199 |
Level 2 [Member] | Sovereign Debt [Member] | Fair Value, Recurring [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Financial instruments owned |  | 1,219,043 |  | 1,038,483 |
Level 2 [Member] | Other [Member] | Fair Value, Recurring [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Financial instruments owned |  | 8,296 | [7] | 11,019 | [8]
Financial instruments sold, but not yet purchased, at fair value | [9] | 473 |  |  |
Level 3 [Member] | Fair Value, Recurring [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Investments |  | 31,268 |  | 30,471 |
Total Assets |  | 72,112 |  | 89,972 |
Financial instruments sold, but not yet purchased, at fair value |  | 1,241 |  | 1,090 |
Total Liabilities |  | 1,241 |  | 1,090 |
Level 3 [Member] | Fair Value, Recurring [Member] | Asset-Backed Securities [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Financial instruments owned |  | 1,034 |  | 1,034 |
Level 3 [Member] | Fair Value, Recurring [Member] | Corporate Equity Securities [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Investments |  | 17,074 |  | 15,565 |
Level 3 [Member] | Fair Value, Recurring [Member] | Auction Rate Securities [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Investments |  | 554 |  | 558 |
Level 3 [Member] | Fair Value, Recurring [Member] | Other Investment [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Investments |  | 13,640 | [5] | 14,348 | [6]
Level 3 [Member] | Sovereign Debt [Member] | Fair Value, Recurring [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Financial instruments owned |  | 40,844 |  | 59,501 |
Level 3 [Member] | Other [Member] | Fair Value, Recurring [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Financial instruments owned |  | 39,810 | [7] | 58,467 | [8]
Financial instruments sold, but not yet purchased, at fair value |  | $ 1,241 | [9] | $ 1,090 | [10]
[1] | Included in other assets in the consolidated statements of financial condition.
[2] | Included in other assets in the consolidated statements of financial condition.
[3] | Included in accounts payable and accrued expenses in the consolidated statements of financial condition.
[4] | Included in accounts payable and accrued expenses in the consolidated statements of financial condition
[5] | Primarily includes private company investments.
[6] | Primarily includes private company investments.
[7] | Includes syndicated loans, non-agency mortgage-backed securities, and sovereign debt.
[8] | Includes syndicated loans, non-agency mortgage-backed securities, and sovereign debt.
[9] | Includes syndicated loans and sovereign debt.
[10] | Includes syndicated loans.

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- Definition Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. 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