Exchangeable Partnership Units

No definition available.

Name:	nmrk_ExchangeablePartnershipUnits
Namespace Prefix:	nmrk_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Exchangeable Preferred Limited Partnership Units, Number Of Tranches

+ References

No definition available.

+ Details

Name:	nmrk_ExchangeablePreferredLimitedPartnershipUnitsNumberOfTranches
Namespace Prefix:	nmrk_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Limited partnership units exchange ratio.

+ References

No definition available.

+ Details

Name:	nmrk_LimitedPartnershipUnitsExchangeRatio
Namespace Prefix:	nmrk_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of profits allocated to preferred partnership units.

+ References

No definition available.

+ Details

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

- Definition

Post termination award payout period.

+ References

No definition available.

+ Details

Name:	nmrk_PostTerminationAwardPayoutPeriod
Namespace Prefix:	nmrk_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of shares converted in a noncash (or part noncash) transaction. Noncash is defined as transactions during a period that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4313-108586

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4304-108586

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4332-108586

+ Details

Name:	us-gaap_ConversionOfStockSharesConverted1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
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

No definition available.

+ Details

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

- Definition

Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_CapitalUnitsByClassAxis=nmrk_NonDistributionEarningUnitsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=us-gaap_CommonClassAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=us-gaap_CommonClassBMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=nmrk_CantorMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ConsolidatedEntitiesAxis=nmrk_NewmarkOpCoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CounterpartyNameAxis=nmrk_TheRoyalBankOfCanadaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Limited Partnership Interests in Newmark Holdings and BGC Holdings (Details)	3 Months Ended				9 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Sep. 30, 2020 tranche shares	Dec. 31, 2019	Dec. 13, 2017
Related Party Transaction
Payout period for post-termination awards					4 years
Percentage to preferred units (in percentage)	0.6875%	0.6875%	0.6875%	0.6875%		2.75%
Non Distribution Earning Units
Related Party Transaction
Award vesting period					4 years
Class A Common Stock
Related Party Transaction
Limited partnership units exchange ratio (in percentage)					0.9373		1
Class B Common Stock \| Cantor
Related Party Transaction
Exchangeable partnership units (in shares)					22,700,000
Share conversion rate (in shares)					1
Newmark OpCo \| RBC
Related Party Transaction
Exchangeable preferred limited partnership units, number of tranches \| tranche					4