Earnings Per Share - Narrative (Detail) - shares shares in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
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	15.9	15.8	15.9
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)			54.2	63.1
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)			54.2	63.1
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)			54.2	63.1
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)	15.4	15.5	15.6	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)			54.2	63.1
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)	0.1	0.4	0.2	0.9