Compensation - Schedule of Activity Associated with Restricted Stock Units (Details) - Restricted Stock Units - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2026	Dec. 31, 2025
Newmark Holdings, L.P.
Restricted Stock Units
Beginning balance (in shares)	9,676,773	10,977,725
Number of units, Granted (in shares)	607,822	3,023,455
Number of Settled units (delivered shares) (in shares)	(1,698,101)	(3,994,549)
Number of Units, Forfeited units (in shares)	(1,921)	(329,858)
Ending balance (in shares)	8,584,573	9,676,773
Weighted- Average Grant Date Fair Value Per Share
Balance at the beginning of period (in dollars per share)	$ 9.84	$ 8.91
Granted (in dollars per share)	17.11	11.84
Settled units (delivered shares) (in dollars per share)	9.74	8.80
Forfeited units (in dollars per share)	16.02	9.86
Balance at the end of period (in dollars per share)	$ 10.37	$ 9.84
Fair Value Amount
Balance at beginning of period	$ 95,173	$ 97,771
Granted	10,398	35,802
Settled units (delivered shares)	(16,541)	(35,147)
Forfeited units	(31)	(3,253)
Balance at end of period	$ 88,999	$ 95,173
Number of shares authorized to be repurchased (in shares)	25,378,000	57,886,000
Newmark Holdings, L.P. | Minimum
Fair Value Amount
Award vesting period	3 years
Newmark Holdings, L.P. | Maximum
Fair Value Amount
Award vesting period	8 years
BGC Holdings, L.P.
Restricted Stock Units
Beginning balance (in shares)	2,270	3,586
Number of units, Granted (in shares)	391	0
Number of Settled units (delivered shares) (in shares)	(780)	(1,316)
Number of Units, Forfeited units (in shares)	0	0
Ending balance (in shares)	1,881	2,270
Weighted- Average Grant Date Fair Value Per Share
Balance at the beginning of period (in dollars per share)	$ 3.96	$ 4.08
Granted (in dollars per share)	5.28	0
Settled units (delivered shares) (in dollars per share)	4.76	4.28
Forfeited units (in dollars per share)	0	0
Balance at the end of period (in dollars per share)	$ 3.90	$ 3.96
Fair Value Amount
Balance at beginning of period	$ 9	$ 15
Granted	2	0
Settled units (delivered shares)	(4)	(6)
Forfeited units	0	0
Balance at end of period	$ 7	$ 9
Number of shares authorized to be repurchased (in shares)	7,000	12,000
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