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, 2025	May 31, 2025	Apr. 30, 2025	Jun. 30, 2024	May 31, 2024	Apr. 30, 2024	Jun. 30, 2025	Mar. 31, 2025	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2025	Jun. 30, 2024
Share issuances:
Treasury stock repurchases (in shares)	(12,000)	(16,115,000)	(1,097,000)	(4,102,000)	(5,031,000)	(1,555,000)	(17,224,000)	(3,184,000)	(10,688,000)	(11,250,000)	(20,408,000)	(21,938,000)
Limited Partnership
Share issuances:
Number of units redeemed and cancelled for exchange (in shares)							400,000		800,000		700,000	1,200,000
Class A Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares outstanding at beginning of period (in shares)			378,134,000			385,134,000	378,134,000	374,297,000	385,134,000	390,095,000	374,297,000	390,095,000
Share issuances:
Redemptions/exchanges of limited partnership interests and contingent share obligations (in shares)							376,000		753,000		617,000	1,118,000
Vesting of RSUs (in shares)							2,254,000		1,975,000		7,078,000	5,685,000
Acquisitions (in shares)							268,257		0		641,653	472,255
Other issuances of BGC Class A common stock (in shares)							2,487,000		2,450,000		4,340,000	4,829,000
Restricted stock forfeitures (in shares)							(101,852)		(36,465)		(372,504)	(672,632)
Treasury stock repurchases (in shares)							(16,127,307)		(9,431,127)		(18,572,136)	(19,251,407)
Shares outstanding at end of period (in shares)	366,193,000			379,588,000			366,193,000	378,134,000	379,588,000	385,134,000	366,193,000	379,588,000
Conversion, shares issued (in shares)							400,000		800,000		600,000	1,100,000