Related Party Transactions - Transactions with Executive Officers and Directors (Howard & Brandon Lutnick) (Details)							1 Months Ended		3 Months Ended		6 Months Ended
	May 16, 2025 $ / shares shares	Feb. 05, 2025 $ / shares shares	Jan. 13, 2025 $ / shares shares	Sep. 23, 2024 $ / shares shares	Jan. 02, 2024 USD ($) shares	Dec. 27, 2021 USD ($)	Jun. 30, 2025 $ / shares shares	May 31, 2025 $ / shares shares	Jun. 30, 2025 $ / shares shares	Jun. 30, 2024 $ / shares shares	Jun. 30, 2025 $ / shares shares	Jun. 30, 2024 $ / shares shares	Jan. 02, 2025 shares	Oct. 23, 2024 USD ($) shares
Related Party Transaction
Share price (in dollars per share) | $ / shares		$ 14.14	$ 11.93	$ 15.34
Stock repurchased (in shares)				795,376
Related party transaction, award payment term						3 years
Class A Common Stock
Related Party Transaction
Treasury stock repurchases (in shares)							0	10,839,674	10,839,674	5,502,703	10,839,674	8,966,102
Shares repurchased price (in dollars per share) | $ / shares							$ 0	$ 11.58	$ 11.58	$ 10.09	$ 11.58	$ 10.34
Stock repurchased, gross (in shares)		2,653,272
Shares withheld for tax withholding obligation (in shares)			232,380
Stock repurchased (in shares)		1,309,367	186,732
Mr. Lutnick
Related Party Transaction
Shares repurchased price (in dollars per share) | $ / shares	$ 11.58
Cash payment | $					$ 1,250,000
Mr. Lutnick | Rights for Previously Non-Exchangeable PSUs
Related Party Transaction
Warrants and rights outstanding (in shares)		1,148,970			617,262								101,133	712,347
Class of warrant or right, number of securities called by warrants or rights (in shares)		1,148,970			617,262								101,133	712,347
Class of warrant or right, issued upon conversion (in shares)		2,859,437
Class of warrant or right, conversion ratio		0.9279
Stock repurchased, gross (in shares)			419,112
Shares withheld for tax withholding obligation (in shares)		1,343,905
Mr. Lutnick | Rights for Monetization of Previously Awarded Nonexchangeable PPSUs
Related Party Transaction
Warrants and rights outstanding (in shares)					81,275									81,275
Class of warrant or right, cash payment called by warrants or rights | $					$ 1,250,000									$ 1,250,000
Mr. Lutnick | Non-Exchangeable Rights for Newmark Holdings PSUs/NPSUs
Related Party Transaction
Class of warrant or right, waived (in shares)					617,262
Mr. Lutnick | Non-Exchangeable Rights for Newmark Holdings PPSUs
Related Party Transaction
Class of warrant or right, waived (in shares)					81,275
Mr. Lutnick | Sale of Class A Common Stock to Company
Related Party Transaction
Treasury stock repurchases (in shares)	10,969,523
Shares repurchased price (in dollars per share) | $ / shares	$ 11.58
Mr. Lutnick | Sale of Class A Common Stock to Company | Howard W. Lutnick, Spouse and Trusts
Related Party Transaction
Treasury stock repurchases (in shares)	10,839,674
Mr. Lutnick | Sale of Class A Common Stock to Company | Mr. Lutnick
Related Party Transaction
Treasury stock repurchases (in shares)	7,989,936
Mr. Lutnick | Sale of Class A Common Stock to Company | Personal Asset Trust
Related Party Transaction
Treasury stock repurchases (in shares)	2,843,781
Mr. Lutnick | Sale of Class A Common Stock to Company | Family Trust
Related Party Transaction
Treasury stock repurchases (in shares)	3,384
Mr. Lutnick | Sale of Class A Common Stock to Company | Spouse
Related Party Transaction
Treasury stock repurchases (in shares)	2,573
Mr. Lutnick | Sale of Class A Common Stock to Company | Retirement Accounts
Related Party Transaction
Treasury stock repurchases (in shares)	129,849
Mr. Lutnick | Retention Bonus Agreement
Related Party Transaction
Aggregate cash payments | $						$ 50,000,000
Mr. Lutnick | Retention Bonus Agreement, Payment Within Three Days
Related Party Transaction
Aggregate cash payments | $						20,000,000
Mr. Lutnick | Retention Bonus Agreement, Payment Within Thirty Days
Related Party Transaction
Aggregate cash payments | $						$ 10,000,000