Stock Transactions and Unit Redemptions - Changes in Shares of Class A Common Stock Outstanding (Detail) - shares	1 Months Ended			3 Months Ended							12 Months Ended
	Dec. 31, 2023	Nov. 30, 2023	Oct. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share issuances:
Redemptions/exchanges of limited partnership interests (in shares)											29,118,664	30,998,136	58,024,858
Restricted stock awards											38,610,233	0
Forfeitures of restricted BGC Class A common stock (in shares)											(1,400,000)	(100,000)
Treasury stock repurchases (in shares)	0	(1,204,000)	(4,269,000)	(8,087,000)	(9,814,000)	(846,000)	(5,945,000)	(12,397,000)	(8,745,000)	0	(24,220,000)	(27,087,000)
Contingent restricted stock awards (in shares)											22,400,000
Limited Partnership
Share issuances:
Common stock, shares issued (in shares)											400,000
Number of units redeemed and cancelled for exchange (in shares)											26,400,000	21,400,000
Class A Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares outstanding at beginning of period (in shares)						325,858,000				317,023,000	325,858,000	317,023,000
Share issuances:
Redemptions/exchanges of limited partnership interests (in shares)											30,754,000	30,998,000
Vesting of RSUs (in shares)											13,009,000	3,284,000
Acquisitions (in shares)											4,566,000	1,206,000
Other issuances of BGC Class A common stock (in shares)											2,946,000	501,000
Forfeitures of restricted BGC Class A common stock (in shares)											(1,428,000)	(67,000)
Treasury stock repurchases (in shares)											(23,250,551)	(27,086,884)	(68,253,498)
Shares outstanding at end of period (in shares)	390,095,000						325,858,000				390,095,000	325,858,000	317,023,000
Common stock, shares issued (in shares)											20,500,000	20,900,000