Compensation - Compensation Expense Related to Limited Partnership Units and Restricted Stock Units (Details) - USD ($)	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Share-based Compensation Arrangement by Share-based Payment Award
Issuance of common stock and exchangeability expenses	$ 36,106,000	$ 24,583,000
Total compensation expense	51,212,000	35,407,000
Equity-based compensation and allocations of net income to limited partnership units and FPUs	51,443,000	35,648,000
Limited Partnership Units
Share-based Compensation Arrangement by Share-based Payment Award
Total compensation expense	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	51,443,000	35,648,000
NEWMARK Group Inc | Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award
Limited partnership units amortization	7,759,000	5,963,000
NEWMARK Group Inc | Limited Partnership Units
Share-based Compensation Arrangement by Share-based Payment Award
Issuance of common stock and exchangeability expenses	36,106,000	21,873,000
Limited partnership units amortization	7,347,000	7,571,000
Allocations of net income to limited partnership units and FPUs	$ 231,000	$ 241,000