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Area of a real estate property.

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Related Party Transactions - Other Related Party Transactions and Cantor Rights to Purchase Cantor Units from Newmark Holdings (Details) ft² in Thousands							1 Months Ended	3 Months Ended		6 Months Ended
	Jun. 30, 2023 USD ($) shares	Apr. 16, 2023 USD ($) shares	Oct. 25, 2022 USD ($) shares	May 17, 2022 USD ($) shares	Jun. 28, 2021 USD ($)	Nov. 30, 2018 USD ($)	Jan. 31, 2022 USD ($) ft²	Jun. 30, 2023 USD ($)	Jun. 30, 2022 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2022 USD ($)	Dec. 31, 2022 USD ($)	Nov. 06, 2018	Dec. 13, 2017
Related Party Transaction
Debt	$ 774,088,000							$ 774,088,000		$ 774,088,000		$ 547,784,000
Operating lease payments										$ 61,400,000	$ 52,900,000
Due from related party, percentage from sale										10.00%
Limited partnership units exchange ratio	0.4545							0.4545		0.4545
Common Stock
Related Party Transaction
Limited partnership units exchange ratio													1
Class A Common Stock
Related Party Transaction
Limited partnership units exchange ratio														1
Class A Common Stock \| NEWMARK Group Inc Parent
Related Party Transaction
Limited partnership units exchange ratio	0.9235							0.9235		0.9235
Related Party
Related Party Transaction
Payables to related parties	$ 9,300,000							$ 9,300,000		$ 9,300,000		$ 9,700,000
Remaining lease terms							6 months
Area of real estate property \| ft²							21
Monthly payment on sublease							$ 81,600
Options to extend leases	3 months							3 months		3 months
Operating lease payments								$ 200,000	$ 200,000	$ 500,000	500,000
Annual base salary					$ 125,000
Annual discretionary bonus rate, maximum					30.00%
Travel and housing reimbursement					$ 250,000
Related Party \| Founding partner interest
Related Party Transaction
Stock issued (in shares) \| shares	74,026	309,631	104,701	184,714
Proceeds from sales of partnership interest	$ 310,976	$ 1,282,265	$ 446,647	$ 763,064
Related Party \| Limited partner interest
Related Party Transaction
Stock issued (in shares) \| shares		38,989	102,454	23,562
Proceeds from sales of partnership interest		$ 166,364	$ 272,100	$ 100,079
Cantor Credit Agreement \| Related Party \| Line of Credit
Related Party Transaction
Maximum revolving credit						$ 250,000,000
Basis spread on variable rate						1.00%
Debt	$ 0							$ 0	$ 0	$ 0	$ 0