Compensation - Activity Associated with Limited Partnership Units (Details) - shares	9 Months Ended	12 Months Ended
	Sep. 30, 2022	Dec. 31, 2021
NEWMARK Group Inc Parent
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding
Beginning balance (in shares)	18,419,613
Number of units, Issued (in shares)	11,734,955
Number of units, Redeemed/exchanged units (in shares)	(599,184)
Number of units, Forfeited units (in shares)	(245,349)
Ending balance (in shares)	29,310,035	18,419,613
Exchangeable units (in shares)	7,526,254	2,468,443
NEWMARK Group Inc Parent | Regular units
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding
Ending balance (in shares)	27,994,887
NEWMARK Group Inc Parent | Preferred Units
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding
Ending balance (in shares)	1,315,148
BGC Holdings, L.P.
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding
Beginning balance (in shares)	8,663,930
Number of units, Issued (in shares)	10,330
Number of units, Redeemed/exchanged units (in shares)	(1,161,440)
Number of units, Forfeited units (in shares)	(60,511)
Ending balance (in shares)	7,452,309	8,663,930
Exchangeable units (in shares)	3,472,610	3,456,479
BGC Holdings, L.P. | Regular units
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding
Ending balance (in shares)	7,370,392
BGC Holdings, L.P. | Preferred Units
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding
Ending balance (in shares)	81,917