Earnings 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		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Fully diluted earnings per share:
Net income available to common stockholders	[1]	$ 85,475	$ 66,563	$ 118,599	$ 87,107
Allocations of net income to limited partnership interests in Newmark Holdings, net of tax		14,025	13,475	3,780	17,473
Net income for fully diluted shares		$ 99,500	$ 80,038	$ 122,379	$ 104,580
Weighted-average shares:
Basic weighted-average shares of common stock outstanding		177,020	155,152	178,122	155,348
Partnership units	[2]	28,466	29,126	5,661	29,356
RSUs		786	157	1,231	196
Other		344	699	399	659
Fully diluted weighted-average shares of common stock outstanding		206,616	185,134	185,413	185,559
Fully diluted earnings per share		$ 0.48	$ 0.43	$ 0.66	$ 0.56

[1] Includes a reduction for dividends on preferred stock or units in the amount of $3.2 million and $1.7 million for the three months ended September 30, 2019 and 2018, respectively, and $9.7 million and $1.9 million for the nine months ended September 30, 2019 and 2018, respectively.

[2] Partnership units collectively include founding/working partner units, limited partnership units, and Cantor units (See Note 2 – “Limited Partnership Interests” for more information).