Related Party Transactions - Service Agreements (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Related Party Transaction [Line Items]
Total revenues	$ 482,694	$ 416,567	$ 1,508,641	$ 1,358,787
Tower Bridge International Services LP \| BGC Partners, Inc.
Related Party Transaction [Line Items]
Company ownership of Tower Bridge			52.00%
Tower Bridge International Services LP \| Cantor
Related Party Transaction [Line Items]
Ownership percentage by noncontrolling owners	48.00%		48.00%
Related Party
Related Party Transaction [Line Items]
Mark-up cost of services			7.50%
Share of net profit (loss) from noncontrolling interest	$ 1,200	200	$ 1,800	0
Compensation to leased employees	16,300	13,700	48,000	43,500
Related Party \| Service Agreement with Cantor
Related Party Transaction [Line Items]
Total revenues	3,700	3,900	11,700	10,800
Service charges	$ 23,300	$ 20,300	$ 71,400	$ 61,800

Percentage mark-up charged to related party for cost of administrative services, technology services or other support.

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Total expense related to fees paid to a related party to cover the compensation costs of leased employees, which is included as "compensation and employee benefits" in the consolidated statements of operations.

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Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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The aggregate total costs related to selling a firm's product and services, as well as all other general and administrative expenses. Direct selling expenses (for example, credit, warranty, and advertising) are expenses that can be directly linked to the sale of specific products. Indirect selling expenses are expenses that cannot be directly linked to the sale of specific products, for example telephone expenses, Internet, and postal charges. General and administrative expenses include salaries of non-sales personnel, rent, utilities, communication, etc.

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Percentage of subsidiary's or equity method investee's stock owned by parent immediately after all stock transactions.

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