Related Party Transactions - Cantor Rights to Purchase Cantor Units from Newmark Holdings (Details)				1 Months Ended			3 Months Ended			12 Months Ended
	Oct. 23, 2024 USD ($) shares	Jun. 30, 2023 USD ($) shares	Apr. 16, 2023 USD ($) shares	Dec. 31, 2024 shares	Nov. 30, 2024 shares	Oct. 31, 2024 shares	Sep. 30, 2024 shares	Jun. 30, 2024 shares	Mar. 31, 2024 shares	Dec. 31, 2024 shares	Dec. 31, 2023 shares	Dec. 31, 2022 shares	Sep. 23, 2024	Nov. 06, 2018	Dec. 13, 2017
Related Party Transaction
Limited partnership units exchange ratio	0.9257			0.4545						0.4545			0.9248
Related Party
Related Party Transaction
General partners' capital account, units outstanding (in shares)				0						0
Founding partner interest | Related Party
Related Party Transaction
Issuance of Class A common stock for Newmark RSUs (in shares)	500,617	74,026	309,631
Proceeds from the sale of limited partnership interests | $	$ 1,824,045	$ 300,000	$ 1,300,000
Founding partner interest | Related Party | Exchangeable Limited Partnership Interests
Related Party Transaction
Unit exercised during period (in shares)	13,861
Unit granted during period (in shares)	12,831
Limited partner interest | Related Party
Related Party Transaction
Issuance of Class A common stock for Newmark RSUs (in shares)	162,086		38,989
Proceeds from the sale of limited partnership interests | $	$ 506,022		$ 200,000
Common Stock
Related Party Transaction
Limited partnership units exchange ratio														1
Class A Common Stock
Related Party Transaction
Limited partnership units exchange ratio															1
Treasury stock repurchases (in shares)				0	1,837,131	146,035	6,779,828	5,502,703	3,463,399	17,729,096	5,785,370	24,918,482
Deferred stock distribution obligations (in shares)										7,221,277
Class A Common Stock | Newmark Holdings Units
Related Party Transaction
Limited partnership units exchange ratio				0.9279						0.9279