Notes Payable, Other and Short-Term Borrowings - Summary Notes Payable, Other and Short-term Borrowings (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	May 25, 2023	Dec. 31, 2022	Jul. 10, 2020	Sep. 27, 2019	Jul. 24, 2018
Debt Instrument [Line Items]
Total Notes payable and other borrowings	$ 1,183,443		$ 1,049,217
Short-term borrowings	0		1,917
Total Notes payable, other and short-term borrowings	1,183,443		1,051,134
BGC Partners 5.375% Senior Notes due July 24, 2023
Debt Instrument [Line Items]
Senior notes	$ 0		449,243
Total Notes payable, other and short-term borrowings						$ 444,200
Stated interest rate	5.375%					5.375%
BGC Partners 3.750% Senior Notes due October 1, 2024
Debt Instrument [Line Items]
Senior notes	$ 299,180		298,558
Total Notes payable, other and short-term borrowings	$ 299,200				$ 296,100
Stated interest rate	3.75%				3.75%
BGC Partners 4.375% Senior Notes due December 15, 2025
Debt Instrument [Line Items]
Senior notes	$ 298,630		298,165
Total Notes payable, other and short-term borrowings	$ 298,600			$ 296,800
Stated interest rate	4.375%			4.375%	4.375%
BGC Partners 8.000% Senior Notes due May 25, 2028
Debt Instrument [Line Items]
Senior notes	$ 346,755		0
Total Notes payable, other and short-term borrowings	$ 346,800	$ 346,600
Stated interest rate	8.00%	8.00%
Collateralized borrowings
Debt Instrument [Line Items]
Collateralized borrowings	$ 0		3,251
Unsecured Credit Agreement | Senior Revolving Credit Agreement
Debt Instrument [Line Items]
Unsecured senior revolving credit agreement	$ 238,878		$ 0