Compensation - Narrative (Detail) $ in Thousands			3 Months Ended		6 Months Ended		12 Months Ended
	Jul. 01, 2023 USD ($) shares	Jun. 30, 2023 USD ($) shares	Jun. 30, 2024 USD ($) shares	Jun. 30, 2023 USD ($) shares	Jun. 30, 2024 USD ($) shares	Jun. 30, 2023 USD ($) shares	Dec. 31, 2023 USD ($) shares	Nov. 22, 2021 shares	Nov. 21, 2021 shares	Jul. 01, 2021 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate number of shares grant of future awards (in shares)			455,000,000.0		455,000,000.0
Number of share-equivalent limited partnership units exchangeable into shares (in shares)			0		0		0
Number of common stock settled per restricted stock unit (in shares)					1
Estimated fair value of restricted stock units | $					$ 5,100
Aggregate estimated fair value of limited partnership units and restricted stock units | $							$ 7,400
Aggregate estimated fair value of deferred compensation awards | $					$ 0		$ 600
Number of shares released the restrictions (in shares)			0	2,100,000	0	2,300,000
Shares withheld to satisfy tax liabilities (in shares)			1,300,000		2,700,000
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issuance of restricted stock upon redemption of limited partnership interests (in shares)	25,300,000	22,500,000
Granted | $					$ 105,060
Unrecognized compensation expense related to unvested | $			$ 209,600		$ 209,600
Unrecognized compensation expense related to unvested recognized period					5 years 10 months 17 days
Weighted- Average Remaining Contractual Term (Years)					5 years 10 months 17 days		5 years 11 months 15 days
Limited partnership units outstanding (in shares)			70,576,000		70,576,000		64,942,000
Share-based payment arrangement, decrease for tax withholding obligation | $	$ 74,000	$ 49,200
Restricted Stock Units (RSUs) | Eligible
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Limited partnership units outstanding (in shares)			25,000,000.0		25,000,000.0
Restricted Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issuance of restricted stock upon redemption of limited partnership interests (in shares)	38,600,000
Granted | $					$ 0
Unrecognized compensation expense related to unvested | $			$ 19,500		$ 19,500
Weighted- Average Remaining Contractual Term (Years)					11 months 23 days		2 years 6 months 18 days
Limited partnership units outstanding (in shares)			16,816,000		16,816,000		27,953,000
Share-based payment arrangement, expense | $			$ 8,900		$ 44,300
Accelerated vesting of restricted stock (in shares)					4,300,000
Accelerated vesting expense | $					$ 25,400
Shares withheld to satisfy tax liabilities (in shares)			1,300,000		2,700,000
Restricted Shares | Eligible
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Limited partnership units outstanding (in shares)			1,100,000		1,100,000
Restricted Stock Units, Tax Account
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock redeemed during period (in shares)	16,300,000
Stock issued during period | $		49,200
Granted | $	$ 74,000	$ 123,100
Unrecognized compensation expense related to unvested | $			$ 80,800		$ 80,800
Vested | $			4,500		$ 8,000
Weighted- Average Remaining Contractual Term (Years)					8 years 4 months 24 days
Share-based payment arrangement, expense | $			$ 5,100		$ 11,100
Restricted BGC Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Limited partnership units outstanding (in shares)			0		0		100,000
Restricted Newmark Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares released the restrictions (in shares)			0	1,100,000	0	1,100,000
Non-exchangeable LPUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock redeemed during period (in shares)	54,000,000	16,900,000
Non-exchangeable FPUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock redeemed during period (in shares)		5,600,000
Non-exchangeable PSU
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock redeemed during period (in shares)	9,900,000	10,600,000
Minimum | Restricted Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares saleable period					5 years
Maximum | Restricted Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares saleable period					10 years
LPUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding (in shares)			0		0		0
Common stock exchangeable basis					1
Limited partnership interests exchange ratio					0.9248
LPUs | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares, restriction period					2 years
LPUs | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares, restriction period					5 years
Newmark | Restricted BGC Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Limited partnership units outstanding (in shares)			0		0		0
Newmark | LPUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Limited partnership units outstanding (in shares)			8,433,000		8,433,000		8,779,000
Newmark | LPUs | REUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Notional value with post-termination pay-out amount | $			$ 700		$ 700		$ 700
Aggregate estimated fair value of limited partnership units | $			$ 300		$ 300		$ 300
BGC Holdings | LPUs | REUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of outstanding limited partnership units, unvested (in shares)			100,000		100,000		100,000
BGC or Newmark | Restricted Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, forfeited (in shares)			0	200,000	200,000	200,000
Class A Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of share-equivalent limited partnership units exchangeable into shares (in shares)			200,000		200,000		200,000
Shares, forfeited (in shares)			36,465	189,726	672,632	238,927
Share-based payment arrangement, decrease for tax withholding obligation | $			$ 10,300		$ 21,200
Stock issued to employees (in shares)			2,300,000	0	4,700,000	0
Class A Common Stock | Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Value of shares withheld | $			$ 16,100	$ 1,400	$ 27,900	$ 7,600
Equity plan | Class A Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized to be delivered pursuant to awards granted (in shares)								500,000,000.0	400,000,000.0	600,000,000.0