Loan And Lease Receivable Brokerage Amount

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Loans Receivable With Fixed Rates Of Interest Percentage

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Percentage Of Ownership Interest Of Loans Receivable

+ References

No definition available.

+ Details

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Namespace Prefix:	nmrk_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage Of Third Party Bank Purchased Loan Value

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Percentage Of Third Party Bank Retaining Loan Value

+ References

No definition available.

+ Details

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Namespace Prefix:	nmrk_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Related party transactions broker fees and commissions.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Income from mortgage banking activities (fees and commissions) and servicing real estate mortgages, credit cards, and other financial assets held by others net of any related impairment of capitalized service costs. Also includes any premiums received in lieu of regular servicing fees on such loans only as earned over the life of the loans.

+ References

No definition available.

+ Details

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

- Definition

Amount, before allowance for credit loss, of financing receivable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 5
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=119407570&loc=SL82919230-210447

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The cash outflow to obtain servicing rights, which contractually entitle the servicer to receive fees and ancillary revenues for performing billing, collection, disbursement and recordkeeping services in connection with a mortgage portfolio. Rights may be obtained via (1) acquisition or assumption of a servicing obligation that does not relate to financial assets of the servicer or its consolidated affiliates; or (2) by originating mortgage loans and then (a) transferring the loans to a Variable Interest Entity (VIE) in a transaction that meets the necessary transfer and classification requirements, or (b) transferring the loans in a transaction that meets the requirements for sale accounting.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=7524895&loc=d3e120260-111741

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3213-108585

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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

No definition available.

+ Details

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- Definition

Reflects the sum of all other revenue and income realized from sales and other transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party during the period.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of revenue, fees and commissions earned from transactions between (a) a parent company and its subsidiaries; (b) subsidiaries of a common parent; (c) an entity and trusts for the benefit of employees, for example, but not limited to, pension and profit-sharing trusts that are managed by or under the trusteeship of the entity's management; (d) an entity and its principal, owners, management, or members of their immediate families; and (e) affiliates.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07.1(c))
-URI http://asc.fasb.org/extlink&oid=116637345&loc=SL114874292-224272

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1(e))
-URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227

+ Details

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

- Definition

The value of new servicing assets, subsequently measured at fair value, acquired or created during the current period through purchases or from transfers of financial assets.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 3
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=116651436&loc=d3e122625-111746

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

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Namespace Prefix:
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- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_RealEstateLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=srt_ChiefExecutiveOfficerMember
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- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=nmrk_CantorCommercialRealEstateCompanyMember
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- Details

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Related Party Transactions - Transactions with CCRE (Details) - USD ($)			3 Months Ended		9 Months Ended
	Aug. 16, 2019	Jul. 22, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Related Party Transaction
Purchase of mortgage servicing rights					$ 200,000	$ 845,000
Mortgage servicing right recognized			$ 30,244,000	$ 34,908,000	78,263,000	70,112,000
Third Party Bank And Cantor Commercial Real Estate LP
Related Party Transaction
Amount of loan purchased by third-party (in percentage)	80.00%
Amount of loan retained by third-party (in percentage)	20.00%
Interest rate on loans receivable (in percentage)	4.38%
Fee paid to Newmark for brokering loan	$ 700,000
Real Estate Loan \| Third Party Bank And Cantor Commercial Real Estate LP
Related Party Transaction
Commercial real estate loan		$ 146,600,000
Primary Servicing Rights
Related Party Transaction
MSR acquired			0
Mr. Gosin \| Third Party Bank And Cantor Commercial Real Estate LP
Related Party Transaction
Ownership interest of loans receivable (in percentage)		19.00%
CCRE
Related Party Transaction
Recognized related party revenues			400,000	100,000	500,000	800,000
CCRE \| Loan Referral Agreement
Related Party Transaction
Revenue from loan referral agreement				700,000		1,600,000
Broker fees and commissions				200,000		400,000
CCRE \| Primary Servicing Rights
Related Party Transaction
MSR acquired				137,000,000.0	227,000,000.0	584,000,000.0
Purchase of mortgage servicing rights				600,000	200,000	800,000
Mortgage servicing right recognized			$ 1,300,000	$ 900,000	$ 3,300,000	$ 2,900,000