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Fair Value Measurements (Tables) | 9 Months Ended
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Sep. 30, 2025
Fair Value Disclosures [Abstract] |
Valuation of Company's Assets and Liabilities Measured at Fair Value | The following table summarizes the valuation of the Company’s assets and liabilities measured at fair value as categorized based on the hierarchy described in Note 2:
| Level 1 |  |  | Level 2 |  |  | Level 3 |  |  | Total |
| (In thousands) |
As of September 30, 2025 |  |  |  |  |  |  |  |  |  |  |
Assets |  |  |  |  |  |  |  |  |  |  |
Money market funds | $ | 27,464 |  |  | $ | — |  |  | $ | — |  |  | $ | 27,464 |
Securities available-for-sale |  |  |  |  |  |  |  |  |  |  |
Corporate debt |  | — |  |  |  | 56,748 |  |  |  | — |  |  |  | 56,748 |
Trading securities |  |  |  |  |  |  |  |  |  |  |
U.S. Treasuries |  | — |  |  |  | 100,503 |  |  |  | — |  |  |  | 100,503 |
Mutual funds held in rabbi trust |  | — |  |  |  | 11,221 |  |  |  | — |  |  |  | 11,221 |
Total assets | $ | 27,464 |  |  | $ | 168,472 |  |  | $ | — |  |  | $ | 195,936 |
Liabilities |  |  |  |  |  |  |  |  |  |  |
Foreign currency forward position |  | — |  |  |  | 499 |  |  |  | — |  |  |  | 499 |
Total liabilities | $ | — |  |  | $ | 499 |  |  | $ | — |  |  | $ | 499 |
As of December 31, 2024 |  |  |  |  |  |  |  |  |  |  |
Assets |  |  |  |  |  |  |  |  |  |  |
Money market funds | $ | 55,473 |  |  | $ | — |  |  | $ | — |  |  | $ | 55,473 |
Securities available-for-sale |  |  |  |  |  |  |  |  |  |  |
Corporate debt |  | — |  |  |  | 55,108 |  |  |  | — |  |  |  | 55,108 |
Trading securities |  |  |  |  |  |  |  |  |  |  |
U.S. Treasuries |  | — |  |  |  | 99,045 |  |  |  | — |  |  |  | 99,045 |
Mutual funds held in rabbi trust |  | — |  |  |  | 11,107 |  |  |  | — |  |  |  | 11,107 |
Total assets | $ | 55,473 |  |  | $ | 165,260 |  |  | $ | — |  |  | $ | 220,733 |
Liabilities |  |  |  |  |  |  |  |  |  |  |
Foreign currency forward position |  | — |  |  |  | 936 |  |  |  | — |  |  |  | 936 |
Total liabilities | $ | — |  |  | $ | 936 |  |  | $ | — |  |  | $ | 936 |
Carrying Value of Financial Asset and Liability Not Measured at Fair Value | The table below presents the carrying value, fair value and fair value hierarchy category of the Company’s financial assets and liabilities that are not measured at fair value on the Consolidated Statements of Financial Condition. The carrying values of the Company’s financial assets and liabilities not measured at fair value categorized in the fair value hierarchy as Level 1 and Level 2 approximate fair value due to the short-term nature of the underlying assets and liabilities.
| Carrying Value |  |  | Fair Value |  |  | Level 1 |  |  | Level 2 |  |  | Level 3 |  |  | Total |
| (In thousands) |
As of September 30, 2025 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Financial assets not measured at fair value: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cash | $ | 445,835 |  |  | $ | 445,835 |  |  | $ | 445,835 |  |  | $ | — |  |  | $ | — |  |  | $ | 445,835 |
Cash segregated under federal regulations |  | 48,351 |  |  |  | 48,351 |  |  |  | 48,351 |  |  |  | — |  |  |  | — |  |  |  | 48,351 |
Accounts receivable, net of allowance |  | 110,519 |  |  |  | 110,519 |  |  |  | — |  |  |  | 110,519 |  |  |  | — |  |  |  | 110,519 |
Receivables from broker-dealers, clearing organizations and customers |  | 606,667 |  |  |  | 606,667 |  |  |  | 119,942 |  |  |  | 486,725 |  |  |  | — |  |  |  | 606,667 |
Total | $ | 1,211,372 |  |  | $ | 1,211,372 |  |  | $ | 614,128 |  |  | $ | 597,244 |  |  | $ | — |  |  | $ | 1,211,372 |
Financial liabilities not measured at fair value: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Payables to broker-dealers, clearing organizations and customers | $ | 365,828 |  |  | $ | 365,828 |  |  | $ | — |  |  | $ | 365,828 |  |  | $ | — |  |  | $ | 365,828 |
As of December 31, 2024 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Financial assets not measured at fair value: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cash | $ | 489,005 |  |  | $ | 489,005 |  |  | $ | 489,005 |  |  | $ | — |  |  | $ | — |  |  | $ | 489,005 |
Cash segregated under federal regulations |  | 47,107 |  |  |  | 47,107 |  |  |  | 47,107 |  |  |  | — |  |  |  | — |  |  |  | 47,107 |
Accounts receivable, net of allowance |  | 91,845 |  |  |  | 91,845 |  |  |  | — |  |  |  | 91,845 |  |  |  | — |  |  |  | 91,845 |
Receivables from broker-dealers, clearing organizations and customers |  | 357,728 |  |  |  | 357,728 |  |  |  | 107,652 |  |  |  | 250,076 |  |  |  | — |  |  |  | 357,728 |
Total | $ | 985,685 |  |  | $ | 985,685 |  |  | $ | 643,764 |  |  | $ | 341,921 |  |  | $ | — |  |  | $ | 985,685 |
Financial liabilities not measured at fair value: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Payables to broker-dealers, clearing organizations and customers | $ | 218,845 |  |  | $ | 218,845 |  |  | $ | — |  |  | $ | 218,845 |  |  | $ | — |  |  | $ | 218,845 |
Summary of Foreign Currency Forward Contracts | The following table summarizes the Company’s foreign currency forward position:
| As of |
| September 30, 2025 |  |  | December 31, 2024 |
| (In thousands) |
Notional value | $ | 67,723 |  |  | $ | 64,454 |
Fair value of notional |  | 67,224 |  |  |  | 63,518 |
Fair value of the (liability) | $ | (499 | ) |  | $ | (936 | )
Summary of Realized and Unrealized Gains and Losses on Foreign Currency Forward Contracts | The following table summarizes the realized and unrealized gains and losses on foreign currency forward contracts:
| Three Months Ended September 30, |  |  | Nine Months Ended September 30, |
| 2025 |  |  | 2024 |  |  | 2025 |  |  | 2024 |
| (In thousands) |
Unrealized gain/(loss) | $ | (2,202 | ) |  | $ | 2,270 |  |  | $ | 438 |  |  | $ | 868 |
Realized gain/(loss) |  | 600 |  |  |  | 1,195 |  |  |  | 3,690 |  |  |  | 1,808 |
Total gain/(loss) | $ | (1,602 | ) |  | $ | 3,465 |  |  | $ | 4,128 |  |  | $ | 2,676 |
Summary of Company's Investments | The following table summarizes the Company’s investments:
| Amortized cost |  |  | Gross unrealized gains |  |  | Gross unrealized losses |  |  | Fair value |
|  | (In thousands) |
As of September 30, 2025 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Securities available-for-sale |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Corporate debt | $ |  | 56,460 |  |  | $ |  | 300 |  |  | $ |  | (12 | ) |  | $ |  | 56,748 |
Trading securities |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
U.S. Treasuries |  |  | 100,270 |  |  |  |  | 254 |  |  |  |  | (21 | ) |  |  |  | 100,503 |
Mutual funds held in rabbi trust |  |  | 10,237 |  |  |  |  | 984 |  |  |  |  | — |  |  |  |  | 11,221 |
Total investments | $ |  | 166,967 |  |  | $ |  | 1,538 |  |  | $ |  | (33 | ) |  | $ |  | 168,472 |
As of December 31, 2024 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Securities available-for-sale |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Corporate debt | $ |  | 55,447 |  |  | $ |  | 88 |  |  | $ |  | (427 | ) |  | $ |  | 55,108 |
Trading securities |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
U.S. Treasuries |  |  | 100,484 |  |  |  |  | 86 |  |  |  |  | (1,525 | ) |  |  |  | 99,045 |
Mutual funds held in rabbi trust |  |  | 10,212 |  |  |  |  | 900 |  |  |  |  | (5 | ) |  |  |  | 11,107 |
Total investments | $ |  | 166,143 |  |  | $ |  | 1,074 |  |  | $ |  | (1,957 | ) |  | $ |  | 165,260 |
Summary of Companies Unrealized and Realized Gains and Losses on Investments | The following table summarizes the Company’s unrealized and realized gains and losses on investments:
| Three Months Ended September 30, |  |  | Nine Months Ended September 30, |
| 2025 |  |  | 2024 |  |  | 2025 |  |  | 2024 |
| (In thousands) |  |  |  |  |
Unrealized gains/(losses) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Securities available-for-sale |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Corporate debt | $ |  | 124 |  |  | $ |  | 324 |  |  | $ |  | 626 |  |  | $ |  | 233 |
Trading securities |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
U.S. Treasuries |  |  | (166 | ) |  |  |  | 845 |  |  |  |  | 1,113 |  |  |  |  | 852 |
Mutual funds held in rabbi trust |  |  | (487 | ) |  |  |  | 505 |  |  |  |  | 90 |  |  |  |  | 1,850 |
Total investments | $ |  | (529 | ) |  | $ |  | 1,674 |  |  | $ |  | 1,829 |  |  | $ |  | 2,935 |
Liabilities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Securities sold, not yet purchased | $ |  | — |  |  | $ |  | (44 | ) |  | $ |  | — |  |  | $ |  | — |
Realized gains/(losses) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Securities available-for-sale |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Corporate debt | $ |  | — |  |  | $ |  | 2 |  |  | $ |  | — |  |  | $ |  | 4 |
Trading securities |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Mutual funds held in rabbi trust |  |  | 1,161 |  |  |  |  | 30 |  |  |  |  | 1,255 |  |  |  |  | (347 | )
Total investments | $ |  | 1,161 |  |  | $ |  | 32 |  |  | $ |  | 1,255 |  |  | $ |  | (343 | )
Liabilities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Securities sold, not yet purchased | $ |  | — |  |  | $ |  | 174 |  |  | $ |  | — |  |  | $ |  | 174 |
Summary of Fair Value of Investments Based upon Contractual Maturities | The following table summarizes the fair value of the Company’s corporate debt and U.S. Treasury investments based upon the contractual maturities:
| Less than one year |  |  | Due in 1 - 5 years |  |  | Total |
| (In thousands) |
As of September 30, 2025 |  |  |  |  |  |  |  |
Securities available-for-sale |  |  |  |  |  |  |  |
Corporate debt | $ | 9,484 |  |  | $ | 47,264 |  |  | $ | 56,748 |
Trading securities |  |  |  |  |  |  |  |
U.S. Treasuries |  | 24,920 |  |  |  | 75,583 |  |  |  | 100,503 |
Total | $ | 34,404 |  |  | $ | 122,847 |  |  | $ | 157,251 |
As of December 31, 2024 |  |  |  |  |  |  |  |
Securities available-for-sale |  |  |  |  |  |  |  |
Corporate debt | $ | 9,346 |  |  | $ | 45,762 |  |  | $ | 55,108 |
Trading securities |  |  |  |  |  |  |  |
U.S. Treasuries |  | 49,978 |  |  |  | 49,067 |  |  |  | 99,045 |
Total | $ | 59,324 |  |  | $ | 94,829 |  |  | $ | 154,153 |
Summary of Fair Values and Unrealized Losses on Investments | The following table provides fair values and unrealized losses on the Company’s available-for-sale investments and the aging of securities’ continuous unrealized loss positions:
| Less than Twelve Months |  |  | Twelve Months or More |  |  | Total |
| Fair value |  |  | Gross unrealized losses |  |  | Fair value |  |  | Gross unrealized losses |  |  | Fair value |  |  | Gross unrealized losses |
| (In thousands) |
As of September 30, 2025 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Corporate debt | $ | 11,467 |  |  | $ | (11 | ) |  | $ | 753 |  |  | $ | (1 | ) |  | $ | 12,220 |  |  | $ | (12 | )
As of December 31, 2024 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Corporate debt | $ | 38,041 |  |  | $ | (426 | ) |  | $ | 1,226 |  |  | $ | (1 | ) |  | $ | 39,267 |  |  | $ | (427 | )

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