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, 2022	Dec. 31, 2021	Dec. 31, 2020
Newmark Holdings, L.P.
Restricted Stock Units
Beginning balance (in shares)		10,721,457	10,646,797
Number of units, Issued (in shares)		3,350,516	2,913,572
Number of Settled units (delivered shares) (in shares)		(2,464,570)	(2,196,903)
Number of units, Forfeited units (in shares)		(343,541)	(642,009)
Ending balance (in shares)		11,263,862	10,721,457	10,646,797
Weighted- Average Grant Date Fair Value Per Share
Balance at the beginning of period (in dollars per share)		$ 8.30	$ 7.75
Granted (in dollars per share)		12.15	9.71
Settled units (delivered shares) (in dollars per share)		8.33	7.64
Forfeited units (in dollars per share)		10.11	7.74
Balance at the end of period (in dollars per share)		$ 9.39	$ 8.30	$ 7.75
Fair Value Amount
Balance at beginning of period		$ 89,025	$ 82,494
Granted		40,710	28,290
Settled units (delivered shares)		(20,526)	(16,792)
Forfeited units		(3,474)	(4,967)
Balance at end of period		$ 105,735	$ 89,025	$ 82,494
Weighted- Average Remaining Contractual Term (Years)		4 years 9 months	4 years 11 months 15 days	5 years 8 months 8 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)		5,375	8,013
Number of units, Issued (in shares)		4,191	0
Number of Settled units (delivered shares) (in shares)		(2,638)	(2,638)
Number of units, Forfeited units (in shares)		0	0
Ending balance (in shares)		6,928	5,375	8,013
Weighted- Average Grant Date Fair Value Per Share
Balance at the beginning of period (in dollars per share)		$ 3.85	$ 3.80
Granted (in dollars per share)		4.28	0
Settled units (delivered shares) (in dollars per share)		3.69	3.69
Forfeited units (in dollars per share)		0	0
Balance at the end of period (in dollars per share)		$ 4.17	$ 3.85	$ 3.80
Fair Value Amount
Balance at beginning of period		$ 21	$ 31
Granted		18	0
Settled units (delivered shares)		(10)	(10)
Forfeited units		0	0
Balance at end of period		$ 29	$ 21	$ 31
Weighted- Average Remaining Contractual Term (Years)		1 year 7 months 13 days	1 year 1 month 28 days	2 years 2 months 1 day
BGC Holdings, L.P. | Minimum
Fair Value Amount
Award vesting period		2 years
BGC Holdings, L.P. | Maximum
Fair Value Amount
Award vesting period		4 years