Notes Payable and Other Borrowings - Carrying Amounts and Estimated Fair Values of Company's Senior Notes (Detail) - USD ($) $ in Thousands	Dec. 31, 2024	Nov. 08, 2024	Aug. 21, 2024	Jun. 10, 2024	Dec. 31, 2023	Oct. 19, 2023	Oct. 06, 2023	May 25, 2023	Jul. 10, 2020	Sep. 27, 2019	Jul. 24, 2018
Debt Instrument [Line Items]
Carrying Amount	$ 1,141,709				$ 944,326
Fair Value	1,182,143				947,301
Stated interest rate							8.00%
BGC Partners 5.375% Senior Notes due July 24, 2023
Debt Instrument [Line Items]
Stated interest rate											5.375%
BGC Group 3.750% Senior Notes due October 1, 2024
Debt Instrument [Line Items]
Carrying Amount	0				254,814
Fair Value	$ 0				249,722
Stated interest rate	3.75%						3.75%
BGC Partners 3.750% Senior Notes due October 1, 2024
Debt Instrument [Line Items]
Carrying Amount	$ 0				44,383
Fair Value	$ 0				43,464
Stated interest rate	3.75%									3.75%
BGC Group 4.375% Senior Notes due December 15, 2025
Debt Instrument [Line Items]
Carrying Amount	$ 287,462				286,729
Fair Value	$ 285,556				276,569
Stated interest rate	4.375%	4.375%				4.375%	4.375%
BGC Partners 4.375% Senior Notes due December 15, 2025
Debt Instrument [Line Items]
Carrying Amount	$ 11,824				11,800
Fair Value	$ 11,740				11,371
Stated interest rate	4.375%								4.375%	4.375%
BGC Group 8.000% Senior Notes due May 25, 2028
Debt Instrument [Line Items]
Carrying Amount	$ 344,620				343,852
Fair Value	$ 369,065				363,274
Stated interest rate	8.00%	8.00%				8.00%	8.00%
BGC Partners 8.000% Senior Notes due May 25, 2028
Debt Instrument [Line Items]
Carrying Amount	$ 2,257		$ 500		2,748
Fair Value	$ 2,416				2,901
Stated interest rate	8.00%		8.00%					8.00%
BGC Group 6.600% Senior Notes due June 10, 2029
Debt Instrument [Line Items]
Carrying Amount	$ 495,546				0
Fair Value	$ 513,366				$ 0
Stated interest rate	6.60%	6.60%		6.60%		6.60%