Compensation - Compensation Expense Related to Issuance of BGC or Newmark Class A Common Stock and Grants of Exchangeability on BGC Holdings and Newmark Holdings LPUs Held by BGC Employees (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
LPUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issuance of common stock and grants of exchangeability	$ 29,943	$ 101,938	$ 63,775	$ 153,904