Notes Payable and Other Borrowings - Carrying Amounts and Estimated Fair Values of Company's Senior Notes (Detail) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024	Aug. 21, 2024	Jun. 10, 2024	Oct. 19, 2023	Oct. 06, 2023	May 25, 2023	Jul. 10, 2020	Sep. 27, 2019
Debt Instrument [Line Items]
Carrying Amount	$ 1,142,341	$ 1,141,709
Fair Value	$ 1,186,227	1,182,143
BGC Group 4.375% Senior Notes due December 15, 2025
Debt Instrument [Line Items]
Stated interest rate	4.375%				4.375%	4.375%
Carrying Amount	$ 287,645	287,462
Fair Value	286,948	285,556
BGC Partners 4.375% Senior Notes due December 15, 2025
Debt Instrument [Line Items]
Stated interest rate								4.375%	4.375%
Carrying Amount	11,830	11,824
Fair Value	$ 11,797	11,740
BGC Group 8.000% Senior Notes due May 25, 2028
Debt Instrument [Line Items]
Stated interest rate	8.00%				8.00%	8.00%
Carrying Amount	$ 344,811	344,620
Fair Value	$ 371,414	369,065
BGC Partners 8.000% Senior Notes due May 25, 2028
Debt Instrument [Line Items]
Stated interest rate	8.00%		8.00%				8.00%
Carrying Amount	$ 2,259	2,257	$ 500
Fair Value	2,431	2,416
BGC Group 6.600% Senior Notes due June 10, 2029
Debt Instrument [Line Items]
Stated interest rate				6.60%
Carrying Amount	495,796	495,546
Fair Value	$ 513,637	$ 513,366