Compensation - Summary of the BGC Holdings and Newmark Holdings LPUs Held by BGC Employees (Detail) - LPUs - shares	Sep. 30, 2023	Dec. 31, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Balance outstanding (in shares)	0	110,348,000
Newmark
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Balance outstanding (in shares)	8,905,000	9,351,000
Regular Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Balance outstanding (in shares)	0
Regular Units | Newmark
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Balance outstanding (in shares)	6,831,000
Preferred Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Balance outstanding (in shares)	0
Preferred Units | Newmark
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Balance outstanding (in shares)	2,074,000