Compensation - Narrative (Detail) $ / shares in Units, $ in Thousands					3 Months Ended		12 Months Ended
	Feb. 05, 2025 $ / shares shares	Jul. 01, 2024 USD ($)	Jul. 01, 2023 shares	Jun. 30, 2023 USD ($)	Mar. 31, 2025 USD ($) shares	Mar. 31, 2024 USD ($) shares	Dec. 31, 2024 USD ($) shares	Nov. 22, 2021 shares	Nov. 21, 2021 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate number of shares grant of future awards (in shares)					434,200,000
Number of share-equivalent limited partnership units exchangeable into shares (in shares)					0		0
Number of common stock settled per restricted stock unit (in shares)					1
Accelerated vesting of restricted stock (in shares)	1,300,000
Shares withheld to satisfy tax liabilities (in shares)					700,000	1,400,000
Tax withholding (in dollars per share) | $ / shares	$ 9.38
Accelerated vesting expense | $					$ 9,000
Estimated fair value of restricted stock units | $					14,100		$ 14,700
Aggregate estimated fair value of deferred compensation awards | $					$ 0		$ 600
Number of shares released the restrictions (in shares)					0	0
Number of restricted stock award settled per common stock (in shares)					1
Restricted Stock, Dividend Eligible
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Limited partnership units outstanding (in shares)					22,300,000		22,900,000
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Limited partnership units outstanding (in shares)					68,782,000		72,498,000
Unrecognized compensation expense related to unvested | $					$ 226,600	$ 168,900
Unrecognized compensation expense related to unvested recognized period (in years)					4 years 9 months	5 years 8 months 4 days
Granted | $					$ 31,055
Weighted-average remaining contractual term (years)					4 years 9 months		4 years 6 months 29 days
Granted (in shares)					3,580,000
Restricted Stock Units, Tax Account
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to unvested | $					$ 65,400	$ 86,000
Granted | $		$ 74,000		$ 49,200
Vested | $					$ 4,800	$ 3,500
Weighted-average remaining contractual term (years)					7 years 9 months 7 days	8 years 7 months 9 days
Share-based payment arrangement, expense | $					$ 4,300	$ 6,000
Restricted Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Limited partnership units outstanding (in shares)					4,083,000		7,304,000
Unrecognized compensation expense related to unvested | $					$ 2,500
Granted | $					$ 0
Weighted-average remaining contractual term (years)					8 months 23 days		7 months 2 days
Share-based payment arrangement, expense | $					$ 4,200	$ 35,500
Accelerated vesting of restricted stock (in shares)						4,300,000
Shares withheld to satisfy tax liabilities (in shares)					700,000
Accelerated vesting expense | $						$ 25,400
Granted (in shares)			38,600,000		0
Restricted Shares | BGC or Newmark
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, forfeited (in shares)					0	200,000
Restricted BGC Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Limited partnership units outstanding (in shares)					0		0
Restricted BGC Stock | Newmark
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Limited partnership units outstanding (in shares)					0		0
Restricted Newmark Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares released the restrictions (in shares)					0	0
Restricted Stock, Dividend Eligible
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Limited partnership units outstanding (in shares)					600,000
Minimum | Restricted Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares saleable period (in years)					5 years
Maximum | Restricted Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares saleable period (in years)					10 years
LPUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Limited partnership interests exchange ratio					0.9271
LPUs | Newmark
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Limited partnership units outstanding (in shares)					2,491,000		2,936,000
Granted (in shares)					0
LPUs | REUs | BGC Holdings
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding (in shares)					100,000		100,000
LPUs | REUs | Newmark
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Notional value with post-termination pay-out amount | $					$ 500		$ 500
Aggregate estimated fair value of limited partnership units | $					$ 200		$ 200
LPUs | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares, restriction period (in years)					2 years
LPUs | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares, restriction period (in years)					5 years
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)					100,000		300,000
Stock issued to employees (in shares)					1,800,000	2,300,000
Share-based payment arrangement, decrease for tax withholding obligation | $					$ 8,500	$ 11,000
Accelerated vesting of restricted stock (in shares)	600,000
Conversion right (in shares)	1
Shares withheld to satisfy tax liabilities (in shares)	700,000
Shares, forfeited (in shares)					270,652	636,167
Class A Common Stock | Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Value of shares withheld | $					$ 19,500	$ 11,800
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)			600,000,000.0					500,000,000.0	400,000,000.0