Earnings Per Share and Weighted-Average Shares Outstanding - Calculation of Fully Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Fully diluted earnings per share:
Net income available to common stockholders	[1]	$ 48,519	$ 435,178	$ 48,881	$ 466,642
Allocations of net income to limited partnership interests in Newmark Holdings, net of tax		14,860	148,567	14,567	159,830
Net income for fully diluted shares		$ 63,379	$ 583,745	$ 63,448	$ 626,472
Weighted-average shares:
Common stock outstanding (in shares)		183,948	185,114	186,401	184,190
Partnership units (units)		58,917	83,122	57,576	83,336
RSUs (Treasury stock method) (units)		3,067	4,149	4,475	3,582
Newmark exchange shares (in shares)		2,053	1,170	2,006	1,195
Fully diluted weighted-average shares of common stock outstanding (in shares)		247,985	273,555	250,458	272,303
Fully diluted earnings per share (in usd per share)		$ 0.26	$ 2.13	$ 0.25	$ 2.30

[1] Includes a reduction for dividends on preferred stock or EPUs in the amount of $4.6 million and $6.2 million for the three and six months ended June 30, 2021, respectively. (see Note 1 — “Organization and Basis of Presentation”).