Stock Transactions and Unit Redemptions - Changes in Shares of Class A Common Stock Outstanding (Detail) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Share issuances:
Redemptions/exchanges of limited partnership interests (in shares)	5,064,529	30,155,970	11,707,619	40,586,915
Restricted stock forfeitures (in shares)	(4,000)	(100,000)	(4,000)	(100,000)
Treasury stock repurchases (in shares)	(8,745,000)	(16,543,000)	(8,745,000)	(17,507,000)
Class A Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares outstanding at beginning of period (in shares)	326,563,000	334,364,000	317,023,000	323,018,000
Share issuances:
Redemptions/exchanges of limited partnership interests (in shares)	5,071,000	30,156,000	11,714,000	40,587,000
Vesting of RSUs (in shares)	589,000	360,000	2,571,000	1,728,000
Acquisitions (in shares)	274,000	537,000	1,186,000	787,000
Other issuances of BGC class A common stock (in shares)	339,000	5,000	342,000	266,000
Restricted stock forfeitures (in shares)	(4,419)	(84,000)	(4,419)	(83,765)
Treasury stock repurchases (in shares)	(8,745,310)	(16,542,535)	(8,745,310)	(17,507,006)
Shares outstanding at end of period (in shares)	324,087,000	348,795,000	324,087,000	348,795,000