Stock Transactions and Unit Redemptions - Changes in Shares of Class A Common Stock Outstanding (Detail) - shares	1 Months Ended			3 Months Ended
	Mar. 31, 2023	Feb. 28, 2023	Jan. 31, 2023	Mar. 31, 2023	Mar. 31, 2022
Share issuances:
Redemptions/exchanges of limited partnership interests (in shares)				13,144,521	6,643,090
Restricted stock forfeitures (in shares)				(13,000)	0
Treasury stock repurchases (in shares)	(846,000)	0	0	(846,000)	0
Limited Partnership
Share issuances:
Number of units redeemed and cancelled for exchange (in shares)				7,300,000	3,300,000
Class A Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares outstanding at beginning of period (in shares)			325,858,000	325,858,000	317,023,000
Share issuances:
Redemptions/exchanges of limited partnership interests (in shares)				13,145,000	6,643,000
Vesting of RSUs (in shares)				2,096,000	1,982,000
Acquisitions (in shares)				658,000	912,000
Other issuances of BGC class A common stock (in shares)				13,000	3,000
Restricted stock forfeitures (in shares)				(49,201)	0
Treasury stock repurchases (in shares)				(845,890)	0
Shares outstanding at end of period (in shares)	340,875,000			340,875,000	326,563,000
Common stock, shares issued (in shares)				6,900,000	3,300,000