Stock Transactions and Unit Redemptions - Changes in Shares of Class A Common Stock Outstanding (Detail) - shares	1 Months Ended					3 Months Ended				6 Months Ended
	Jun. 30, 2024	May 31, 2024	Apr. 30, 2024	Jun. 30, 2023	Apr. 30, 2023	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023
Share issuances:
Redemptions/exchanges of limited partnership interests (in shares)								15,974,143			29,118,664
Treasury stock repurchases (in shares)	(4,102,000)	(5,031,000)	(1,555,000)	(3,428,000)	(3,086,000)	(10,688,000)	(11,250,000)	(9,814,000)	(846,000)	(21,938,000)	(10,660,000)
Contingent restricted stock issued (in shares)										15,900,000
Limited Partnership
Share issuances:
Number of units redeemed and cancelled for exchange (in shares)						800,000		19,100,000		1,200,000	26,400,000
Class A Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares outstanding at beginning of period (in shares)			385,134,000		340,875,000	385,134,000	390,095,000	340,875,000	325,858,000	390,095,000	325,858,000
Share issuances:
Redemptions/exchanges of limited partnership interests (in shares)						753,000		17,082,000		1,118,000	30,226,000
Vesting of RSUs (in shares)						1,975,000		534,000		5,685,000	2,630,000
Acquisitions (in shares)						0		3,494,000		472,255	4,152,000
Other issuances of BGC class A common stock (in shares)						2,450,000		(3,000)		4,829,000	11,000
Restricted stock forfeitures (in shares)						(36,465)		(189,726)		(672,632)	(238,927)
Treasury stock repurchases (in shares)						(9,431,127)		(9,813,827)		(19,251,407)	(10,659,717)
Shares outstanding at end of period (in shares)	379,588,000			351,978,000		379,588,000	385,134,000	351,978,000	340,875,000	379,588,000	351,978,000
Conversion, shares issued (in shares)						800,000		13,300,000		1,100,000	20,200,000