Compensation - Activity Associated with Restricted Stock Units (Details) - Restricted Stock Units - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Jan. 01, 2018	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Newmark Holdings, L.P.
Restricted Stock Units
Beginning balance (in shares)		11,263,862	10,721,457
Number of units, Issued (in shares)		4,192,685	3,350,516
Number of Settled units (delivered shares) (in shares)		(2,708,902)	(2,464,570)
Number of units, Forfeited units (in shares)		(614,540)	(343,541)
Ending balance (in shares)		12,133,105	11,263,862	10,721,457
Weighted- Average Grant Date Fair Value Per Share
Balance at the beginning of period (in dollars per share)		$ 9.39	$ 8.30
Granted (in dollars per share)		6.82	12.15
Settled units (delivered shares) (in dollars per share)		9.03	8.33
Forfeited units (in dollars per share)		9.14	10.11
Balance at the end of period (in dollars per share)		$ 8.59	$ 9.39	$ 8.30
Fair Value Amount
Balance at beginning of period		$ 105,735	$ 89,025
Granted		28,594	40,710
Settled units (delivered shares)		(24,461)	(20,526)
Forfeited units		(5,617)	(3,474)
Balance at end of period		$ 104,251	$ 105,735	$ 89,025
Weighted- Average Remaining Contractual Term (Years)		4 years 3 days	4 years 9 months	4 years 11 months 15 days
Newmark Holdings, L.P. | Minimum
Fair Value Amount
Award vesting period	2 years
Newmark Holdings, L.P. | Maximum
Fair Value Amount
Award vesting period	9 years
BGC Holdings, L.P.
Restricted Stock Units
Beginning balance (in shares)		6,928	5,375
Number of units, Issued (in shares)		0	4,191
Number of Settled units (delivered shares) (in shares)		(2,045)	(2,638)
Number of units, Forfeited units (in shares)		0	0
Ending balance (in shares)		4,883	6,928	5,375
Weighted- Average Grant Date Fair Value Per Share
Balance at the beginning of period (in dollars per share)		$ 4.17	$ 3.85
Granted (in dollars per share)		0	4.28
Settled units (delivered shares) (in dollars per share)		4.05	3.69
Forfeited units (in dollars per share)		0	0
Balance at the end of period (in dollars per share)		$ 4.22	$ 4.17	$ 3.85
Fair Value Amount
Balance at beginning of period		$ 29	$ 21
Granted		0	18
Settled units (delivered shares)		(8)	(10)
Forfeited units		0	0
Balance at end of period		$ 21	$ 29	$ 21
Weighted- Average Remaining Contractual Term (Years)		10 months 13 days	1 year 7 months 13 days	1 year 1 month 28 days
BGC Holdings, L.P. | Minimum
Fair Value Amount
Award vesting period		2 years
BGC Holdings, L.P. | Maximum
Fair Value Amount
Award vesting period		3 years