Related Party Transactions - Other Agreements with Cantor (Details)						3 Months Ended		9 Months Ended
	Jul. 01, 2023 shares	Mar. 20, 2020	Nov. 23, 2018 USD ($) shares	Aug. 06, 2018 USD ($)	Jun. 05, 2015 shares	Sep. 30, 2023 USD ($) shares	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) shares	Sep. 30, 2022 USD ($)	Dec. 31, 2022 USD ($)	Jun. 05, 2022	Mar. 19, 2018 USD ($)	Aug. 31, 2013 USD ($)
Related Party Transaction [Line Items]
Reverse repurchase agreements						$ 0		$ 0		$ 0
Commissions						350,305,000	$ 299,430,000	1,076,313,000	$ 965,636,000
Investment in asset-backed commercial paper program						0		0		0
Common stock, exchange ratio			1								1
Conversion of stock, shares converted (in shares) | shares	64,000,000
Minimum number of shares required to be issued (in shares) | shares	75,000,000
Interest expense						20,780,000	14,499,000	56,436,000	43,144,000
Cantor
Related Party Transaction [Line Items]
Repurchase agreements						$ 0		$ 0		0
Class B Common Stock | Cantor
Related Party Transaction [Line Items]
Investment owned, balance (in shares) | shares						93,300,000		93,300,000
Class B Common Stock | CFGM
Related Party Transaction [Line Items]
Investment owned, balance (in shares) | shares						3,000,000		3,000,000
Class A Common Stock | Cantor
Related Party Transaction [Line Items]
Investment owned, balance (in shares) | shares						0		0
Class A Common Stock | CFGM
Related Party Transaction [Line Items]
Investment owned, balance (in shares) | shares						0		0
Related Party
Related Party Transaction [Line Items]
Reverse repurchase agreements						$ 0		$ 0		0
Recognition of share of FX gains						2,100,000	(1,600,000)	(2,800,000)	(3,600,000)
Commissions						100,000	100,000	200,000	300,000
Investment authorization in asset-backed commercial paper program													$ 350,000,000
Right to exchange from Class A to Class B common stock (up to) (in shares) | shares					34,600,000
Common stock, issued during the period, additional consideration			$ 0
Related Party | Cantor
Related Party Transaction [Line Items]
Right to exchange from Class A to Class B common stock (up to) (in shares) | shares			10,300,000
Related Party | CFGM
Related Party Transaction [Line Items]
Right to exchange from Class A to Class B common stock (up to) (in shares) | shares			700,000
Related Party | Revolving credit facility | BGC Credit Agreement
Related Party Transaction [Line Items]
Principal amount of debt component												$ 250,000,000
Related Party | Revolving credit facility | Amendment to BGC Credit Agreement
Related Party Transaction [Line Items]
Principal amount of debt component				$ 400,000,000								$ 250,000,000
Debt instrument, extended term				1 year
Debt instrument, non-extension notice term				6 months
Debt instrument, basis spread on variable rate		1.00%
Line of credit facility, current borrowing capacity						0		0		$ 0
Interest expense						$ 0	$ 0	$ 0	$ 0
Related Party | Maximum
Related Party Transaction [Line Items]
Right to exchange from Class A to Class B common stock (up to) (in shares) | shares					34,600,000