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
		Mar. 31, 2022	Mar. 31, 2021
Fully diluted earnings per share:
Net income available to common stockholders	[1]	$ 362	$ 31,464
Allocations of net income to limited partnership interests in Newmark Holdings, net of tax		76	12,461
Net income for fully diluted shares		$ 438	$ 43,925
Weighted-average shares:
Common stock outstanding (in shares)		188,881	183,254
Partnership units (units)		56,220	83,556
RSUs (Treasury stock method) (units)		5,757	3,165
Newmark exchange shares (in shares)		1,957	1,219
Fully diluted weighted-average shares of common stock outstanding (in shares)		252,815	271,194
Fully diluted earnings per share (in usd per share)		$ 0.00	$ 0.16

[1] Includes a reduction for dividends on preferred stock or EPUs in the amount $1.6 million for the three months ended March 31, 2021. (see Note 1 — “Organization and Basis of Presentation”).