Derivatives - Schedule of Gains Losses on Derivative Contracts Included in Condensed Consolidated Statements of Operations (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Derivative Instruments, Gain (Loss)
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income, net	Other income, net	Other income, net	Other income, net
Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss)
Gain (loss) recognized in income for derivatives	$ (2,708)	$ 12,789	$ 126	$ 19,756
Not Designated as Hedging Instrument \| Rate lock commitments \| Capital markets
Derivative Instruments, Gain (Loss)
Gain (loss) recognized in income for derivatives	1,107	(7,167)	3,136	(100)
Not Designated as Hedging Instrument \| Rate lock commitments \| Compensation and employee benefits
Derivative Instruments, Gain (Loss)
Gain (loss) recognized in income for derivatives	(363)	1,238	(833)	(558)
Not Designated as Hedging Instrument \| Forward Sales Contracts
Derivative Instruments, Gain (Loss)
Gain (loss) recognized in income for derivatives	$ (3,452)	$ 18,718	$ (2,177)	$ 20,414

Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4A
-Subparagraph (b)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-4A

+ Details

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

- Definition

Indicates line item in statement of income or comprehensive income that includes gain (loss) from derivative.

+ References

+ Details

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

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4E
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-4E

+ Details

Name:	us-gaap_DerivativeInstrumentsGainLossLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_HedgingDesignationAxis=us-gaap_NondesignatedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateLockCommitmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementLocationAxis=nmrk_GainsFromCapitalMarketsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementLocationAxis=nmrk_CostOfServicesDirectLaborMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_ForwardContractsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: