Earnings Per Share - Narrative (Detail) - shares shares in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 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)	17.0	0.0
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)	60.2	45.7
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)	60.2	45.7
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)	60.2	45.7
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)	14.4
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)	60.2	45.7
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)	2.6