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, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Fully diluted earnings per share:
Net income available to common stockholders	$ 9,947	$ 27,964	$ 6,027	$ 76,848
Allocations of net income to limited partnership interests in Newmark Holdings, net of tax	4,128	9,710	2,266	23,635
Net income for fully diluted shares	$ 14,075	$ 37,674	$ 8,293	$ 100,483
Weighted-average shares:
Common stock outstanding (in shares)	174,129	177,231	173,549	183,311
Partnership units (units)	71,125	61,501	68,658	58,899
RSUs (Treasury stock method) (units)	1,463	2,604	1,193	3,809
Newmark exchange shares (in shares)	523	2,133	482	2,048
Fully diluted weighted-average shares of common stock outstanding (in shares)	247,240	243,469	243,882	248,067
Fully diluted earnings per share (in usd per share)	$ 0.06	$ 0.15	$ 0.03	$ 0.41