Compensation - Activity Associated with Limited Partnership Units (Details) - shares	6 Months Ended	12 Months Ended
Jun. 30, 2023	Dec. 31, 2022
NEWMARK Group Inc Parent
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding
Beginning balance (in shares)	30,687,954	18,419,613
Number of units, Issued (in shares)	9,697,379	15,402,041
Number of units, Redeemed/exchanged units (in shares)	(1,730,819)	(2,934,984)
Number of units, Forfeited units (in shares)	(217,246)	(198,716)
Ending balance (in shares)	38,437,268	30,687,954
Exchangeable units (in shares)	9,082,995	7,861,359
NEWMARK Group Inc Parent \| Limited Partnership Units
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding
Beginning balance (in shares)	3,900,000
Ending balance (in shares)	3,459,228	3,900,000
Exchangeable partnership units (in shares)	1,690,266	1,500,000
NEWMARK Group Inc Parent \| Limited Partnership Units \| Employee
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding
Ending balance (in shares)	1,853,111
BGC Holdings, L.P.
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding
Beginning balance (in shares)	5,459,388	8,663,930
Number of units, Issued (in shares)	1,506	25,032
Number of units, Redeemed/exchanged units (in shares)	(5,082,356)	(3,169,063)
Number of units, Forfeited units (in shares)	(999)	(60,511)
Ending balance (in shares)	377,539	5,459,388
Exchangeable units (in shares)	68,139	2,654,749
BGC Holdings, L.P. \| Limited Partnership Units
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding
Beginning balance (in shares)	4,800,000
Ending balance (in shares)	73,245	4,800,000
Exchangeable partnership units (in shares)	14,386	2,500,000
BGC Holdings, L.P. \| Limited Partnership Units \| Employee
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding
Ending balance (in shares)	31,945

Exchangeable Partnership Units

No definition available.

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- Definition

Exchangeable Units

+ References

No definition available.

+ Details

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- Definition

Number of exchangeable limited partnership units redeemed or exchanged into the Company's class A common stock during the period.

+ References

No definition available.

+ Details

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- Definition

Number of shares under non-option equity instrument agreements that were cancelled as a result of occurrence of a terminating event.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(3)
-SubTopic 10
-Topic 718
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

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- Definition

Net number of non-option equity instruments granted to participants.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(1)
-SubTopic 10
-Topic 718
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

+ Details

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- Definition

Number of equity instruments other than options outstanding, including both vested and non-vested instruments.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(i)
-SubTopic 10
-Topic 718
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(ii)
-SubTopic 10
-Topic 718
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

+ Details

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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