Compensation - Activity Associated with Limited Partnership Units Awarded to BGC Employees (Detail) - LPUs - shares	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of units, redeemed (in shares)	61,000	11,053,000
BGC Holdings LPUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of units, redeemed (in shares)	0	10,975,000
Newmark Holdings LPUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of units, redeemed (in shares)	61,000	78,000