Schedule I - Parent Company Only - Long Term Debt - Additional Information (Detail) - USD ($)			6 Months Ended		12 Months Ended
	Feb. 26, 2020	Sep. 27, 2019	Dec. 31, 2023	Jun. 30, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Jul. 10, 2020	Nov. 28, 2018	Jul. 24, 2018
Debt Instrument [Line Items]
Total					$ 157,560,000
Redemption price as percentage of principal amount		101.00%
Debt, Long-term and Short-term, Combined Amount			$ 1,183,506,000		1,183,506,000	$ 1,051,134,000
Interest expense					$ 77,231,000	57,932,000	$ 69,329,000
Parent Company
Debt Instrument [Line Items]
Interest expense			$ 17,528,000	$ 30,700,000		53,652,000	60,772,000
BGC Partners 5.375% Senior Notes due July 24, 2023
Debt Instrument [Line Items]
Stated interest rate			5.375%		5.375%
BGC Partners 5.375% Senior Notes due July 24, 2023 | Parent Company
Debt Instrument [Line Items]
Total					$ 14,500,000	25,500,000	25,500,000
Principal amount of notes										$ 450,000,000
Redemption price as percentage of principal amount					101.00%
Debt, Long-term and Short-term, Combined Amount										444,200,000
Debt issuance costs										$ 5,800,000
Stated interest rate										5.375%
BGC Partners 3.750% Senior Notes due October 1, 2024
Debt Instrument [Line Items]
Total					$ 9,500,000	12,100,000	12,100,000
Stated interest rate		3.75%	3.75%		3.75%
BGC Partners 3.750% Senior Notes due October 1, 2024 | Parent Company
Debt Instrument [Line Items]
Principal amount of notes		$ 300,000,000
Debt, Long-term and Short-term, Combined Amount		296,100,000	$ 44,400,000		$ 44,400,000
Debt issuance costs		$ 3,900,000
Stated interest rate		3.75%
BGC Partners 4.375% Senior Notes due December 15, 2025
Debt Instrument [Line Items]
Total					10,500,000
Principal amount of notes								$ 300,000,000
Debt, Long-term and Short-term, Combined Amount			$ 11,800,000		$ 11,800,000			296,800,000
Debt issuance costs								$ 3,200,000
Interest expense						13,800,000	13,800,000
Stated interest rate		4.375%	4.375%		4.375%			4.375%
New Senior Revolving Credit Agreement | Unsecured Credit Agreement November 28, 2018 | Parent Company
Debt Instrument [Line Items]
Maximum revolving credit									$ 350,000,000
Debt instrument, renewal term	2 years
Line of credit facility, outstanding amount			$ 239,200,000		$ 239,200,000	0
Total					$ 6,900,000	$ 2,300,000	$ 3,600,000