Schedule I - Parent Company Only Financial Statements - Accounts Payable and Accrued Expenses - Components of Accounts Payable, Accrued Expenses and Other Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accounts Payable And Accrued Expenses [Line Items]
Corporate taxes payable	$ 77,858	$ 6,697
NEWMARK Group Inc Parent [Member]
Accounts Payable And Accrued Expenses [Line Items]
Accrued interest	5,149	1,254
Corporate taxes payable	79,079	7,059
Other	208	8,000
Accounts Payable and Accrued Liabilities	$ 84,436	$ 16,313