Securities Loaned	12 Months Ended
	Dec. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Securities Loaned	Securities LoanedAs of December 31, 2020 and 2019, Newmark had Securities loaned with Cantor of $33.3 million and $36.7 million, respectively. The market value of the Securities loaned as of December 31, 2020 and 2019 were $32.6 million and $36.8 million, respectively. The cash collateral received from Cantor bore an interest rate of 0.85% and 2.45% as of December 31, 2020 and 2019, respectively.