Securities Loaned	9 Months Ended
	Sep. 30, 2020
Investments, Debt and Equity Securities [Abstract]
Securities Loaned	Securities LoanedAs of September 30, 2020, Newmark did not have Securities loaned with Cantor. As of December 31, 2019, Newmark had Securities loaned with Cantor of $36.7 million. The market value of the Securities loaned as of December 31, 2019 was $36.8 million.