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, 2024	Mar. 31, 2023
Fully diluted earnings per share:
Net loss available to common stockholders	$ (16,254)	$ (10,350)
Allocations of net income to limited partnership interests in Newmark Holdings, net of tax	0	0
Net loss for fully diluted shares	$ (16,254)	$ (10,350)
Weighted-average shares:
Common stock outstanding (in shares)	174,774	172,561
Partnership units (in shares)	0	0
RSUs (Treasury stock method) (in shares)	0	0
Newmark exchange shares (in shares)	0	0
Fully diluted weighted-average shares of common stock outstanding (in shares)	174,774	172,561
Fully diluted earnings per share (in usd per share)	$ (0.09)	$ (0.06)