Stock Transactions and Unit Redemptions - Changes in Shares of Class A Common Stock Outstanding (Detail) - shares	1 Months Ended						3 Months Ended
	Mar. 31, 2025	Feb. 28, 2025	Jan. 31, 2025	Mar. 31, 2024	Feb. 29, 2024	Jan. 31, 2024	Mar. 31, 2025	Mar. 31, 2024
Share issuances:
Treasury stock repurchases (in shares)	(13,000)	0	(3,171,000)	(1,055,000)	(6,586,000)	(3,609,000)	(3,184,000)	(11,250,000)
Limited Partnership
Share issuances:
Number of units redeemed and cancelled for exchange (in shares)							300,000	400,000
Class A Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares outstanding at beginning of period (in shares)			374,297,000			390,095,000	374,297,000	390,095,000
Share issuances:
Redemptions/exchanges of limited partnership interests and contingent share obligations (in shares)							243,000	364,000
Vesting of RSUs (in shares)							4,823,000	3,710,000
Acquisitions (in shares)							373,396	472,255
Other issuances of BGC Class A common stock (in shares)							1,853,000	2,379,000
Restricted stock forfeitures (in shares)							(270,652)	(636,167)
Treasury stock repurchases (in shares)							(2,444,829)	(9,820,280)
Shares outstanding at end of period (in shares)	378,134,000			385,134,000			378,134,000	385,134,000
Conversion, shares issued (in shares)							200,000	400,000