Related Party Transactions - Service Agreements (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
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%
Cantor
Related Party Transaction [Line Items]
Mark-up cost of services	7.50%
Less: Net income (loss) from continuing operations attributable to noncontrolling interest in subsidiaries	$ 0.7	$ 2.5	$ 0.8
Recognized related party revenues	14.7	14.9	25.8
Service charges	84.9	81.9	62.6
Compensation to leased employees	$ 59.2	$ 57.9	$ 39.4

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 after tax of income (loss) from continuing operations attributable to the noncontrolling interest.

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The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.

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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.

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Amount of selling, general and administrative expenses resulting from transactions, excluding transactions that are eliminated in consolidated or combined financial statements, with related party.

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Amount of revenue, fees and commissions earned from transactions between (a) a parent company and its subsidiaries; (b) subsidiaries of a common parent; (c) an entity and trusts for the benefit of employees, for example, but not limited to, pension and profit-sharing trusts that are managed by or under the trusteeship of the entity's management; (d) an entity and its principal, owners, management, or members of their immediate families; and (e) affiliates.

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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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