Related Party Transactions - Transactions with Executive Officers and Directors (Barry Gosin) (Details)			3 Months Ended
	Aug. 07, 2024 USD ($) shares	Feb. 10, 2023 USD ($) installment tranche $ / shares shares	Mar. 31, 2026 USD ($) shares	Feb. 05, 2025 $ / shares	Jan. 13, 2025 $ / shares
Related Party Transaction
Share price (in dollars per share) | $ / shares				$ 14.14	$ 11.93
Mr. Gosin
Related Party Transaction
Related party transaction, termination notice, period	6 months
Related party transaction, one time cash payment	$ 5,000,000
Related party transaction, annual compensation	17,500,000
Related party transaction, annual compensation, salary	1,000,000
Related party transaction, annual compensation, cash-based and share-based awards	$ 16,500,000
Annual cash bonus		$ 1,500,000
Newmark Holdings NPSUs | Mr. Gosin
Related Party Transaction
Number of conversion rights granted (in shares) | shares	1,694,915		1,145,476
Conversion percentage		25.00%	25.00%
Class of warrant or right percentage			75.00%
Minimum gross revenue threshold		$ 10,000,000	$ 10,000,000
Class of warrant or right, rights exchanged (in shares) | shares			1,238,620
Number of tranches | tranche		4
Class of warrant or right, advance award (in shares) | shares		1,145,476
Related party transaction, upfront advance award, base for calculating number of grants in period		$ 10,000,000
Conversion percentage, tranche one		25.00%
Share price (in dollars per share) | $ / shares		$ 8.73
Number of installments | installment		3
Conversion percentage, tranche four		25.00%
Conversion percentage, tranche three		25.00%
Conversion percentage, tranche two		25.00%
Newmark Holdings NPSUs | Mr. Gosin | Award Period One
Related Party Transaction
Share-based liabilities paid	$ 5,000,000
Newmark Holdings NPSUs | Mr. Gosin | Award Period Two
Related Party Transaction
Share-based liabilities paid	15,000,000
Newmark Holdings NPSUs | Mr. Gosin | Award Period Three
Related Party Transaction
Share-based liabilities paid	$ 1,500,000