Notes Payable and Other Borrowings - Carrying Amounts and Estimated Fair Values of Company's Senior Notes (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Oct. 06, 2023	May 25, 2023	Jul. 10, 2020	Sep. 27, 2019
Debt Instrument [Line Items]
Carrying Amount	$ 944,961	$ 944,326
Fair Value	$ 959,120	947,301
BGC Group 3.750% Senior Notes due October 1, 2024
Debt Instrument [Line Items]
Stated interest rate	3.75%		3.75%
Carrying Amount	$ 255,056	254,814
Fair Value	$ 251,233	249,722
BGC Partners 3.750% Senior Notes due October 1, 2024
Debt Instrument [Line Items]
Stated interest rate	3.75%					3.75%
Carrying Amount	$ 44,410	44,383
Fair Value	$ 43,727	43,464
BGC Group 4.375% Senior Notes due December 15, 2025
Debt Instrument [Line Items]
Stated interest rate	4.375%		4.375%
Carrying Amount	$ 286,908	286,729
Fair Value	$ 280,373	276,569
BGC Partners 4.375% Senior Notes due December 15, 2025
Debt Instrument [Line Items]
Stated interest rate	4.375%				4.375%	4.375%
Carrying Amount	$ 11,802	11,800
Fair Value	$ 11,527	11,371
BGC Group 8.000% Senior Notes due May 25, 2028
Debt Instrument [Line Items]
Stated interest rate	8.00%		8.00%
Carrying Amount	$ 344,039	343,852
Fair Value	$ 369,311	363,274
BGC Partners 8.000% Senior Notes due May 25, 2028
Debt Instrument [Line Items]
Stated interest rate	8.00%			8.00%
Carrying Amount	$ 2,746	2,748
Fair Value	$ 2,949	$ 2,901