Notes Payable, Other and Short-term Borrowings - Carrying Amounts and Estimated Fair Values of Company's Senior Notes (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Oct. 06, 2023	May 25, 2023	Dec. 31, 2022	Jul. 10, 2020	Sep. 27, 2019
Debt Instrument [Line Items]
Carrying Amount	$ 944,326			$ 1,045,966
Fair Value	947,301			1,017,015
BGC Partners 5.375% Senior Notes due July 24, 2023
Debt Instrument [Line Items]
Carrying Amount	0			449,243
Fair Value	$ 0			449,007
Stated interest rate	5.375%
BGC Group 3.750% Senior Notes due October 1, 2024
Debt Instrument [Line Items]
Carrying Amount	$ 254,814			0
Fair Value	$ 249,722			0
Stated interest rate	3.75%	3.75%
BGC Partners 3.750% Senior Notes due October 1, 2024
Debt Instrument [Line Items]
Carrying Amount	$ 44,383			298,558
Fair Value	$ 43,464			286,894
Stated interest rate	3.75%					3.75%
BGC Group 4.375% Senior Notes due December 15, 2025
Debt Instrument [Line Items]
Carrying Amount	$ 286,729			0
Fair Value	$ 276,569			0
Stated interest rate	4.375%	4.375%
BGC Partners 4.375% Senior Notes due December 15, 2025
Debt Instrument [Line Items]
Carrying Amount	$ 11,800			298,165
Fair Value	$ 11,371			281,114
Stated interest rate	4.375%				4.375%	4.375%
BGC Partners 8.000% Senior Notes due May 25, 2028
Debt Instrument [Line Items]
Carrying Amount	$ 2,748			0
Fair Value	$ 2,901			0
Stated interest rate	8.00%		8.00%
BGC Group 8.000% Senior Notes due May 25, 2028
Debt Instrument [Line Items]
Carrying Amount	$ 343,852			0
Fair Value	$ 363,274			$ 0
Stated interest rate		8.00%