Compensation - Schedule of Compensation Expense Related to Limited Partnership Units and Restricted Stock Units (Details) - USD ($)	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Share-based Compensation Arrangement by Share-based Payment Award
Issuance of common stock and exchangeability expenses	$ 58,284,000	$ 52,279,000
Total compensation expense	0	0
Equity-based compensation and allocations of net income to limited partnership units and FPUs	68,396,000	74,346,000
Newmark Holdings Units
Share-based Compensation Arrangement by Share-based Payment Award
Total compensation expense	65,515,000	74,166,000
Equity-based compensation and allocations of net income to limited partnership units and FPUs	68,396,000	74,346,000
Newmark Holdings Units | Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award
Limited partnership units amortization	9,554,000	12,348,000
Newmark Holdings Units | Limited Partnership Units
Share-based Compensation Arrangement by Share-based Payment Award
Issuance of common stock and exchangeability expenses	58,284,000	52,279,000
Limited partnership units amortization	(2,323,000)	9,539,000
Allocations of net income to limited partnership units and FPUs	$ 2,881,000	$ 180,000