Name:	nmrk_ContractuallySpecifiedServicingFeesAncillaryFeesEscrowInterestAndPlacementFeesEarnedInExchangeForServicingFinancialAssets
Namespace Prefix:	nmrk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Escrow interest and placement fees amount.

No definition available.

Name:	nmrk_EscrowInterestAndPlacementFeesAmount
Namespace Prefix:	nmrk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

All amounts that are due to the servicer of a financial asset, excluding contractually specified servicing fees and late fees.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 860
-SubTopic 50
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481229/860-50-50-2

Name:	us-gaap_AncillaryFeeIncomeGeneratedByServicingFinancialAssetsAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Indicates line item in statement of income or comprehensive income that includes ancillary fee income from servicing financial asset.

Name:	us-gaap_AncillaryFeeIncomeServicingFinancialAssetStatementOfIncomeOrComprehensiveIncomeExtensibleEnumeration
Namespace Prefix:	us-gaap_
Data Type:	enum2:enumerationSetItemType
Balance Type:	na
Period Type:	duration

Indicates line item in statement of income or comprehensive income that includes contractually specified servicing fee income.

Name:	us-gaap_ContractuallySpecifiedServicingFeeIncomeStatementOfIncomeOrComprehensiveIncomeExtensibleEnumeration
Namespace Prefix:	us-gaap_
Data Type:	enum2:enumerationSetItemType
Balance Type:	na
Period Type:	duration

All amounts that, per contract, are due to the servicer in exchange for servicing the financial asset and would no longer be received by a servicer if the beneficial owners of the serviced assets (or their trustees or agents) were to exercise their actual or potential authority under the contract to shift the servicing to another servicer. Depending on the servicing contract, those fees may include some or all of the difference between the interest rate collected on the asset being serviced and the rate to be paid to the beneficial owners of the asset.

Name:	us-gaap_ContractuallySpecifiedServicingFeesAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- References

No definition available.