Escrow and Custodial Funds	3 Months Ended
	Mar. 31, 2022
Deposit Assets Disclosure [Abstract]
Escrow and Custodial Funds	Escrow and Custodial FundsIn conjunction with the servicing of multifamily and commercial loans, Newmark holds escrow and other custodial funds. Escrow funds are held at unaffiliated financial institutions generally in the form of cash and cash equivalents. These funds amounted to $1.0 billion and $2.3 billion, as of March 31, 2022 and December 31, 2021, respectively. These funds are held for the benefit of Newmark’s borrowers and are segregated in custodial bank accounts. These amounts are excluded from the assets and liabilities of Newmark.