Investments - Equity Method Investments and Investments Carried Under Measurement Alternative (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 40,041	$ 38,122
Investments carried under measurement alternative	192	192
Total equity method and investments carried under measurement alternative	$ 40,233	38,314
Advanced Markets Holdings
Schedule of Equity Method Investments [Line Items]
Investment ownership percentage amount	25.00%
Equity method investments	$ 4,457	4,481
China Credit BGC Money Broking Company Limited
Schedule of Equity Method Investments [Line Items]
Investment ownership percentage amount	33.00%
Equity method investments	$ 23,825	21,277
Freedom International Brokerage
Schedule of Equity Method Investments [Line Items]
Investment ownership percentage amount	45.00%
Equity method investments	$ 9,659	9,507
Other
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 2,100	$ 2,857