Stock Transactions and Unit Redemptions - Schedule of Changes in Shares of Common Stock Outstanding (Details) - shares	1 Months Ended				3 Months Ended				9 Months Ended
	Sep. 30, 2023	Aug. 31, 2023	Jul. 31, 2023	Jul. 31, 2022	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Share issuances:
Other (in shares)					0			(26,742)
Class A Common Stock
Increase (Decrease) in Stockholders' Equity
Shares outstanding at beginning of period (in shares)			152,234,598	160,002,640	152,234,598		150,384,605	160,002,640	150,384,605	168,272,371
Share issuances:
LPU redemption/exchange (in shares)					564,180			421,320	3,650,431	1,983,495
Issuance of Class A common stock for Newmark RSUs (in shares)					1,069,447			0	1,069,447	1,767,736
Other (in shares)									(154,189)	38,093
Treasury stock repurchases (in shares)	(2,787,291)	0	0	(2,787,291)	(2,787,291)	(2,354,217)	0	(10,163,677)	(5,141,508)	(23,217,195)
Shares outstanding at end of period (in shares)	151,461,689				151,461,689	152,234,598		150,530,807	151,461,689	150,530,807
Class A Common Stock | Restricted Stock Units
Share issuances:
Issuance of Class A common stock for Newmark RSUs (in shares)					380,755			297,266	1,652,903	1,686,307