Compensation - Activity Associated with Limited Partnership Units (Details) - shares	6 Months Ended	12 Months Ended
	Jun. 30, 2024	Dec. 31, 2023
NEWMARK Group Inc
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding
Beginning balance (in shares)	42,376,966	30,687,954
Number of units, Issued (in shares)	9,040,073	16,092,841
Number of units, Redeemed/exchanged units (in shares)	(2,462,482)	(3,676,057)
Number of units, Forfeited units/other (in shares)	(398,037)	(727,772)
Ending balance (in shares)	48,556,520	42,376,966
Exchangeable units (in shares)	13,382,806	12,189,148
NEWMARK Group Inc | Limited Partnership Units
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding
Beginning balance (in shares)	3,100,000
Ending balance (in shares)	2,800,000	3,100,000
Exchangeable partnership units (in shares)	1,900,000	1,500,000
NEWMARK Group Inc | Limited Partnership Units | Employee
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding
Ending balance (in shares)	2,200,000
BGC Holdings, L.P.
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding
Beginning balance (in shares)	0	5,459,388
Number of units, Issued (in shares)	0	1,506
Number of units, Redeemed/exchanged units (in shares)	0	(5,459,895)
Number of units, Forfeited units/other (in shares)	0	(999)
Ending balance (in shares)	0	0
Exchangeable units (in shares)	0	0
BGC Holdings, L.P. | Limited Partnership Units
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding
Ending balance (in shares)	0