Schedule I - Parent Company Only - Other Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Condensed Financial Statements, Captions [Line Items]
Derivative assets	$ 32,259	$ 51,021
Prepaid expenses	18,900	15,251
Total other current assets	63,790	91,194
NEWMARK Group Inc Parent
Condensed Financial Statements, Captions [Line Items]
Derivative assets	184,714	179,501
Prepaid expenses	3,534	312
Total other current assets	$ 188,248	$ 179,813