Compensation - Compensation Expense Related to Limited Partnership Units and Restricted Stock Units (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Share-based Compensation Arrangement by Share-based Payment Award
Issuance of common stock and exchangeability expenses	$ 11,852,000	$ 5,832,000	$ 47,958,000	$ 27,705,000
Total compensation expense	24,941,000	19,487,000	76,153,000	54,894,000
Equity-based compensation and allocations of net income to limited partnership units and FPUs			76,929,000	55,258,000
Limited Partnership Units
Share-based Compensation Arrangement by Share-based Payment Award
Total compensation expense	0	0	0	0
NEWMARK Group Inc
Share-based Compensation Arrangement by Share-based Payment Award
Equity-based compensation and allocations of net income to limited partnership units and FPUs	25,486,000	19,609,000	76,929,000	55,258,000
NEWMARK Group Inc | Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award
Limited partnership units amortization	5,920,000	6,221,000	13,679,000	12,184,000
NEWMARK Group Inc | Limited Partnership Units
Share-based Compensation Arrangement by Share-based Payment Award
Issuance of common stock and exchangeability expenses	11,852,000	5,832,000	47,958,000	27,705,000
Limited partnership units amortization	7,169,000	7,434,000	14,516,000	15,005,000
Allocations of net income to limited partnership units and FPUs	$ 545,000	$ 122,000	$ 776,000	$ 364,000