Cover Page - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2021	Apr. 25, 2022	Jun. 30, 2021
Document Information [Line Items]
Document Type	10-K/A
Document Annual Report	true
Document Transition Report	false
Document Period End Date	Dec. 31, 2021
Entity File Number	001-38329
Entity Registrant Name	NEWMARK GROUP, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	81-4467492
Entity Address, Address Line One	125 Park Avenue
Entity Address, City or Town	New York
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	10017
City Area Code	212
Local Phone Number	372-2000
Title of 12(b) Security	Class A Common Stock, $0.01 par value
Trading Symbol	NMRK
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 1.9
Amendment Description	Throughout this document Newmark Group, Inc. is referred to as “Newmark,” and, together with its subsidiaries, as the “Company,” “we,” “us,” or “our.” On March 1, 2022, Newmark filed its Annual Report on Form 10-K for the fiscal year ended December 31, 2021 (the “Original Form 10-K”). Certain Part III information was omitted from the Original Form 10-K in reliance on General Instruction G(3) to Form 10-K. General Instruction G(3) to Form 10-K provides that registrants may incorporate by reference certain information from a definitive proxy statement which involves the election of directors if such definitive proxy statement is filed with the Securities and Exchange Commission within 120 days after the end of the fiscal year. The Company does not anticipate that its definitive proxy statement involving the election of directors in connection with its 2022 annual meeting of stockholders will be filed by April 30, 2022 (i.e., within 120 days after the end of the Company’s 2021 fiscal year). Accordingly, this Amendment No. 1 (this “Amendment”) hereby amends and restates Part III, Items 10 through 14, of the Original Form 10-K as set forth below. The information included herein as required by Part III, Items 10 through 14, of the Original Form 10-K is more limited than what is required to be included in the definitive proxy statement to be filed in connection with our 2022 annual meeting of stockholders. Accordingly, the definitive proxy statement to be filed at a later date will include additional information related to the topics herein and additional information not required by Part III, Items 10 through 14, of Form 10-K. This Amendment also restates Item 15 of Part IV of the Original Form 10-K. In addition, as required by Rule 12b-15 under the Securities Exchange Act of 1934, as amended, new certifications by our principal executive officer and principal financial officer are filed as exhibits to this Amendment under Item 15 of Part IV hereof. No other amendments are being made hereby to the Original Form 10-K. Except as stated herein, this Amendment does not reflect events occurring after the filing of the Original Form 10-K with the Securities and Exchange Commission on March 1, 2022, and no attempt has been made in this Amendment to modify or update other disclosures as presented in the Original Form 10-K.
Amendment Flag	true
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Entity Central Index Key	0001690680
Current Fiscal Year End Date	--12-31
Auditor Name	Ernst & Young, LLP
Auditor Firm ID	42
Auditor Location	New York, New York
Common Class A [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		164,678,443
Common Class B [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		21,285,533