Compensation - Summary of the BGC Holdings and Newmark Holdings LPUs held by BGC Employees (Detail) - LPUs - shares	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of units, balance outstanding (in shares)	0	110,348,000	112,115,000	137,652,000
Newmark
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of units, balance outstanding (in shares)	8,779,000	9,351,000	11,051,000	13,202,000
Regular Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of units, balance outstanding (in shares)	0
Regular Units | Newmark
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of units, balance outstanding (in shares)	6,742,000
Preferred Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of units, balance outstanding (in shares)	0
Preferred Units | Newmark
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of units, balance outstanding (in shares)	2,037,000