Related Party Transactions - Other Agreements with Cantor (Details) shares in Millions					3 Months Ended		6 Months Ended
	Mar. 20, 2020	Nov. 23, 2018 USD ($) shares	Aug. 06, 2018 USD ($)	Jun. 05, 2015 shares	Jun. 30, 2023 USD ($)	Jun. 30, 2022 USD ($)	Jun. 30, 2023 USD ($) shares	Jun. 30, 2022 USD ($)	Dec. 31, 2022 USD ($)	Jun. 05, 2022	Mar. 19, 2018 USD ($)	Aug. 31, 2013 USD ($)
Related Party Transaction [Line Items]
Commissions					$ 348,720,000	$ 309,542,000	$ 726,008,000	$ 666,206,000
Common stock, exchange ratio		1								1
Interest expense					19,914,000	14,342,000	35,656,000	28,645,000
Reverse repurchase agreements					200,000,000		200,000,000		$ 0
Cantor
Related Party Transaction [Line Items]
Repurchase agreements					0		0		0
Related Party
Related Party Transaction [Line Items]
Recognition of share of FX gains					3,500,000	2,400,000	4,900,000	2,000,000
Commissions					0	100,000	0	200,000
Investment authorization in asset-backed commercial paper program												$ 350,000,000
Investment in asset-backed commercial paper program					0		0		0
Right to exchange from Class A to Class B common stock (up to) (in shares) | shares				34.6
Common stock, issued during the period, additional consideration		$ 0
Reverse repurchase agreements					200,000,000		200,000,000		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		10.3
Related Party | CFGM
Related Party Transaction [Line Items]
Right to exchange from Class A to Class B common stock (up to) (in shares) | shares		0.7
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 | Class B Common Stock
Related Party Transaction [Line Items]
Right to exchange from Class A to Class B common stock (up to) (in shares) | shares							23.6
Related Party | Maximum
Related Party Transaction [Line Items]
Right to exchange from Class A to Class B common stock (up to) (in shares) | shares				34.6			23.6