Earnings Per Share - Narrative (Detail) - shares shares in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share amount (in shares)	15.9	114.2	15.9	120.0
Contingent Class A Common Stock | BGC Holdings Partnership Unit
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share amount (in shares)			63.1	39.6
Contingent Class A Common Stock | Limited Partnership Unit
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share amount (in shares)			63.1	39.6
Contingent Class A Common Stock | N Units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share amount (in shares)			63.1	39.6
Restricted Stock Units (RSUs)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share amount (in shares)	15.5		15.0
Restricted Stock Units (RSUs) | Contingent Class A Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share amount (in shares)			63.1	39.6
Earnings RSAs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share amount (in shares)	0.4		0.9