Aggregate dividends declared during the period for each share of common stock outstanding.

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Schedule I - Parent Company Only - Subsequent Events (Detail) - USD ($)	Feb. 26, 2020	Feb. 12, 2020	Nov. 28, 2018	Nov. 22, 2017
NEWMARK Group Inc Parent \| Subsequent Event
Subsequent Event [Line Items]
Common stock dividends per share declared (in dollars per share)		$ 0.10
Revolving Credit Facility
Subsequent Event [Line Items]
Maximum revolving credit				$ 400,000,000.0
Line of Credit \| Revolving Credit Facility
Subsequent Event [Line Items]
Maximum revolving credit			$ 250,000,000.0
Line of Credit \| Revolving Credit Facility \| Subsequent Event
Subsequent Event [Line Items]
Maximum revolving credit	$ 425,000,000.0
Line of Credit \| Revolving Credit Facility \| NEWMARK Group Inc Parent
Subsequent Event [Line Items]
Maximum revolving credit			$ 250,000,000.0
LIBOR \| Line of Credit \| Revolving Credit Facility \| Subsequent Event
Subsequent Event [Line Items]
Basis spread on variable rate	1.75%