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		9 Months Ended
		Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Fully diluted earnings per share:
Net income available to common stockholders	[1]	$ 27,964	$ 128,549	$ 76,848	$ 595,198
Allocations of net income to limited partnership interests in Newmark Holdings, net of tax		9,710	0	23,635	0
Net income for fully diluted shares		$ 37,674	$ 128,549	$ 100,483	$ 595,198
Weighted-average shares:
Common stock outstanding (in shares)		177,231	199,413	183,311	189,317
Partnership units (units)		61,501		58,899	0
RSUs (Treasury stock method) (units)		2,604	4,696	3,809	3,816
Newmark exchange shares (in shares)		2,133	1,172	2,048	1,187
Fully diluted weighted-average shares of common stock outstanding (in shares)		243,469	205,281	248,067	194,320
Fully diluted earnings per share (in usd per share)		$ 0.15	$ 0.63	$ 0.41	$ 3.06

[1] Includes a reduction for dividends on preferred stock or EPUs in the amount of $0.0 million and $6.2 million for the three and nine months ended September 30, 2021, respectively. (see Note 1 — “Organization and Basis of Presentation”).