Compensation - Activity Associated with Restricted Stock Units (Details) - Restricted Stock Units - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Newmark Holdings, L.P.
Restricted Stock Units
Beginning balance (in shares)	10,977,725	12,133,105
Number of units, Granted (in shares)	311,983	2,838,998
Number of Settled units (delivered shares) (in shares)	(2,114,503)	(3,118,150)
Number of Units, Forfeited units (in shares)	(109,546)	(876,228)
Ending balance (in shares)	9,065,659	10,977,725	12,133,105
Weighted- Average Grant Date Fair Value Per Share
Balance at the beginning of period (in dollars per share)	$ 8.91	$ 8.59
Granted (in dollars per share)	12.44	9.92
Settled units (delivered shares) (in dollars per share)	8.96	8.61
Forfeited units (in dollars per share)	9.62	8.89
Balance at the end of period (in dollars per share)	$ 9.01	$ 8.91	$ 8.59
Fair Value Amount
Balance at beginning of period	$ 97,771	$ 104,251
Granted	3,882	28,159
Settled units (delivered shares)	(18,946)	(26,850)
Forfeited units	(1,054)	(7,789)
Balance at end of period	$ 81,653	$ 97,771	$ 104,251
Weighted- Average Remaining Contractual Term (Years)	3 years 11 months 4 days	3 years 9 months 29 days	4 years 3 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)	3,586	4,883
Number of units, Granted (in shares)	0	19,425
Number of Settled units (delivered shares) (in shares)	(1,241)	(1,243)
Number of Units, Forfeited units (in shares)	0	(19,479)
Ending balance (in shares)	2,345	3,586	4,883
Weighted- Average Grant Date Fair Value Per Share
Balance at the beginning of period (in dollars per share)	$ 4.08	$ 4.22
Granted (in dollars per share)	0	6.87
Settled units (delivered shares) (in dollars per share)	4.28	4.28
Forfeited units (in dollars per share)	0	6.88
Balance at the end of period (in dollars per share)	$ 3.97	$ 4.08	$ 4.22
Fair Value Amount
Balance at beginning of period	$ 15	$ 21
Granted	0	133
Settled units (delivered shares)	(5)	(5)
Forfeited units	0	(134)
Balance at end of period	$ 10	$ 15	$ 21
Weighted- Average Remaining Contractual Term (Years)	2 months 1 day	3 months 29 days	10 months 13 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