Compensation - Activity Associated with Limited Partnership Units Awarded to BGC Employees (Detail) - LPUs - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of units, redeemed (in shares)	14,810,000	4,962,000	25,863,000	11,013,000
BGC Holdings LPUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of units, redeemed (in shares)	14,710,000	4,879,000	25,684,000	10,666,000
Newmark Holdings LPUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of units, redeemed (in shares)	100,000	83,000	179,000	347,000