Related Party Transactions - Other Agreements with Cantor (Details)						3 Months Ended
	Mar. 12, 2024 USD ($)	Mar. 11, 2024	Jul. 01, 2023 shares	Aug. 06, 2018 USD ($)	Jun. 05, 2015 shares	Mar. 31, 2024 USD ($) shares	Mar. 31, 2023 USD ($)	Dec. 31, 2023 USD ($)	Mar. 19, 2018 USD ($)	Aug. 31, 2013 USD ($)
Related Party Transaction [Line Items]
Reverse repurchase agreements						$ 0		$ 0
Commissions						415,172,000	$ 377,288,000
Limited partnership interest, conversion ratio					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						$ 20,136,000	15,742,000
New Senior Revolving Credit Agreement | Unsecured Credit Agreement
Related Party Transaction [Line Items]
Average interest rate						7.19%
Line of credit facility, outstanding amount						$ 0		239,200,000
Class B Common Stock | Cantor
Related Party Transaction [Line Items]
Investment owned, balance (in shares) | shares						93,300,000
Class B Common Stock | CFGM
Related Party Transaction [Line Items]
Investment owned, balance (in shares) | shares						3,000,000
Class A Common Stock | Cantor
Related Party Transaction [Line Items]
Investment owned, balance (in shares) | shares						0
Class A Common Stock | CFGM
Related Party Transaction [Line Items]
Investment owned, balance (in shares) | shares						0
Related Party
Related Party Transaction [Line Items]
Repurchase agreements						$ 0		0
Reverse repurchase agreements						0		0
Recognition of share of FX gains						(100,000)	1,300,000
Commissions						100,000	100,000
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
Related Party | Revolving credit facility
Related Party Transaction [Line Items]
Interest expense						1,100,000	$ 0
Related Party | Revolving credit facility | BGC Credit Agreement
Related Party Transaction [Line Items]
Principal amount of debt component									$ 250,000,000
Debt instrument, non-extension notice term				6 months
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
Line of credit facility, current borrowing capacity								$ 0
Proceeds from credit facility	$ 275,000,000
Line of credit facility, outstanding amount	$ 240,000,000					$ 275,000,000
Related Party | Revolving credit facility | Amendment to BGC Credit Agreement | Unsecured Credit Agreement November Twenty Eight Two Thousand Eighteen, Loans Made Under Credit Agreement
Related Party Transaction [Line Items]
Debt instrument, basis spread on variable rate		0.25%
Interest rate		6.92%				6.92%
Related Party | New Senior Revolving Credit Agreement | BGC Credit Agreement | Unsecured Credit Agreement
Related Party Transaction [Line Items]
Interest rate		7.17%
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