Notes Payable and Other Borrowings - Carrying Amounts and Estimated Fair Values of Company's Senior Notes (Detail) - USD ($) $ in Thousands	Jun. 30, 2024	Jun. 10, 2024	Dec. 31, 2023	Oct. 06, 2023	May 25, 2023	Jul. 10, 2020	Sep. 27, 2019
Debt Instrument [Line Items]
Carrying Amount	$ 1,440,689		$ 944,326
Fair Value	$ 1,462,995		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	$ 255,306		254,814
Fair Value	$ 253,717		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	$ 44,444		44,383
Fair Value	$ 44,159		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	$ 287,096		286,729
Fair Value	$ 281,295		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	$ 11,812		11,800
Fair Value	$ 11,565		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	$ 344,236		343,852
Fair Value	$ 372,345		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	$ 2,751		2,748
Fair Value	2,974		2,901
BGC Group 6.600% Senior Notes due June 10, 2029
Debt Instrument [Line Items]
Stated interest rate		6.60%
Carrying Amount	495,044		0
Fair Value	$ 496,940		$ 0