Earnings (Loss) Per Share and Weighted-Average Shares Outstanding - Calculation of Fully Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Fully diluted earnings (loss) per share:
Net income (loss) available to common stockholders	[1]	$ (2,131)	$ 19,444	$ 3,604	$ 33,124
Allocations of net income (loss) to limited partnership interests in Newmark Holdings, net of tax		0	3,864	0	0
Net income (loss) for fully diluted shares		$ (2,131)	$ 23,308	$ 3,604	$ 33,124
Weighted-average shares:
Common stock outstanding (in shares)		178,523	178,754	178,034	178,683
Partnership units (units)		0	28,769	0	0
RSUs (Treasury stock method) (units)		0	228	442	324
Newmark exchange shares (shares)		0	399	234	427
Fully diluted weighted-average shares of common stock outstanding (in shares)		178,523	208,150	178,710	179,434
Fully diluted earnings (loss) per share (in usd per share)		$ (0.01)	$ 0.11	$ 0.02	$ 0.18

[1] ⁽¹⁾  Includes a reduction for dividends on preferred stock or exchangeable preferred partnership units in the amount of $2.4 million and $4.9 million for the three and six months ended June 30, 2020, respectively, and $3.2 million and $6.4 million for the three and six months ended June 30, 2019, respectively (see Note 1 — “Organization and Basis of Presentation”).