Stock Transactions and Unit Redemptions - Changes in Shares of Class A Common Stock Outstanding (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Share issuances:
Redemptions/exchanges of limited partnership interests (in shares)	11,939,546	8,446,093	23,647,165	49,033,008
Restricted stock forfeitures (in shares)	(43,000)	(56,000)	(47,000)	(140,000)
Treasury stock repurchases (in shares)	(12,397,000)	(24,433,000)	(21,142,000)	(41,940,000)
Limited Partnership
Share issuances:
Number of units redeemed and cancelled for exchange (in shares)	6,000,000	6,900,000	14,100,000	23,200,000
Class A Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares outstanding at beginning of period (in shares)	324,087,000	348,795,000	317,023,000	323,018,000
Share issuances:
Redemptions/exchanges of limited partnership interests (in shares)	11,940,000	8,446,000	23,654,000	49,033,000
Vesting of RSUs (in shares)	451,000	213,000	3,022,000	1,941,000
Acquisitions (in shares)	0	343,000	1,186,000	1,130,000
Other issuances of BGC class A common stock (in shares)	98,000	100,000	441,000	366,000
Restricted stock forfeitures (in shares)	(43,388)	(56,423)	(47,807)	(140,188)
Treasury stock repurchases (in shares)	(12,396,735)	(24,432,718)	(21,142,045)	(41,939,724)
Shares outstanding at end of period (in shares)	324,136,000	333,408,000	324,136,000	333,408,000
Common stock, shares issued (in shares)	5,800,000	5,800,000	13,700,000	21,200,000