Stock Transactions and Unit Redemptions - Changes in Shares of Class A Common Stock Outstanding (Detail) - shares	1 Months Ended						3 Months Ended						9 Months Ended
	Sep. 30, 2023	Aug. 31, 2023	Jul. 31, 2023	Sep. 30, 2022	Aug. 31, 2022	Jul. 31, 2022	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023	Sep. 30, 2022
Share issuances:
Redemptions/exchanges of limited partnership interests (in shares)										11,939,546			29,118,664	23,647,165
Acquisitions (in shares)														1,192,907
Restricted stock issuances (in shares)							38,610,233			0			38,610,233	0
Treasury stock repurchases (in shares)	(3,474,000)	(1,612,000)	(3,000,000)	(3,448,000)	(5,916,000)	(3,033,000)	(8,087,000)	(9,814,000)	(846,000)	(12,397,000)	(8,745,000)	0	(18,747,000)	(21,142,000)
Contingent restricted stock issued (in shares)							26,600,000						26,600,000
Limited Partnership
Share issuances:
Number of units redeemed and cancelled for exchange (in shares)							200,000			6,000,000			26,400,000	14,100,000
Class A Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares outstanding at beginning of period (in shares)			351,978,000			324,087,000	351,978,000		325,858,000	324,087,000		317,023,000	325,858,000	317,023,000
Share issuances:
Redemptions/exchanges of limited partnership interests (in shares)							346,000			11,940,000			30,572,000	23,654,000
Vesting of RSUs (in shares)							6,145,000			451,000			8,775,000	3,022,000
Acquisitions (in shares)							413,884			0			4,566,000	1,186,000
Other issuances of BGC class A common stock (in shares)							461,000			98,000			472,000	441,000
Restricted stock forfeitures (in shares)							0			(43,388)			(238,927)	(47,807)
Treasury stock repurchases (in shares)							(8,086,750)			(12,396,735)			(18,746,467)	(21,142,045)
Shares outstanding at end of period (in shares)	389,867,000			324,136,000			389,867,000	351,978,000		324,136,000	324,087,000		389,867,000	324,136,000
Conversion, shares issued (in shares)							200,000			5,800,000			20,400,000	13,700,000