Condensed Consolidated Statements of Changes in Equity (Parenthetical) - shares	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Common Stock \| Class A Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Grant of exchangeability, redemption and issuance of limited partnership interests and issuance of common stock (in shares)	436,285	498,129

Grant of exchangeability, redemption and issuance of limited partnership interests and issuance of common stock, shares.

No definition available.

Name:	nmrk_GrantOfExchangeabilityRedemptionAndIssuanceOfLimitedPartnershipInterestsAndIssuanceOfCommonStockShares
Namespace Prefix:	nmrk_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration