Compensation - Limited Partnership Units with a Post-Termination Payout (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2024	Dec. 31, 2023
BGC Holdings, L.P.
Share-based Compensation Arrangement by Share-based Payment Award
Notional Value	$ 162,619	$ 158,594
Estimated fair value of the post-termination payout	$ 62,314	$ 54,950
Newmark Holdings Units
Share-based Compensation Arrangement by Share-based Payment Award
Outstanding limited partnership units (in shares)	17,231,737	16,704,405
Outstanding limited partnership units - unvested (in dollars per share)	335,808	4,856,908