Compensation - Narrative (Detail) $ in Thousands	3 Months Ended		6 Months Ended		9 Months Ended	12 Months Ended
	Jun. 30, 2023 USD ($) shares	Jun. 30, 2022 USD ($) shares	Jun. 30, 2023 USD ($) shares	Jun. 30, 2022 USD ($) shares	Sep. 30, 2022 USD ($)	Dec. 31, 2022 USD ($) 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)	90,000,000		90,000,000
Number of share-equivalent limited partnership units exchangeable into shares (in shares)	200,000		200,000			1,200,000
Number of common stock settled per restricted stock unit (in shares)			1
Aggregate estimated fair value of limited partnership units and restricted stock units | $			$ 5,800		$ 5,900
Aggregate estimated fair value of deferred compensation awards | $			$ 200			$ 23,900
Shares, forfeited (in shares)	200,000	0	200,000	0
Number of shares released the restrictions (in shares)	2,100,000	100,000	2,300,000	200,000
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to unvested | $	$ 123,100		$ 123,100
Unrecognized compensation expense related to unvested recognized period			5 years 6 months
Limited partnership units outstanding (in shares)	34,767,000		34,767,000			12,046,000
Granted | $			$ 95,340
Weighted- Average Remaining Contractual Term (Years)			5 years 5 months 26 days			2 years 5 months 1 day
Restricted Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Limited partnership units outstanding (in shares)	100,000		100,000			2,300,000
Restricted Stock Units, Tax Account
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to unvested | $	$ 48,200		$ 48,200
Granted | $	49,200
Weighted- Average Remaining Contractual Term (Years)						9 years 3 months 18 days
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]
Common stock exchangeable basis			1
Limited partnership interests exchange ratio			0.9235
Unrecognized compensation expense related to unvested | $	$ 84,000		$ 84,000
Unrecognized compensation expense related to unvested recognized period			1 year 11 months 12 days
Limited partnership units outstanding (in shares)	71,594,000		71,594,000			110,347,000
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
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares released the restrictions (in shares)	1,100,000	100,000	1,100,000	100,000
Number of outstanding restricted shares held (in shares)	0		0			1,100,000
Newmark | LPUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Limited partnership units outstanding (in shares)	9,003,000		9,003,000			9,351,000
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 unvested limited partnership units with post-termination pay-out (in shares)	200,000		200,000			800,000
Notional value with post-termination pay-out amount | $	$ 1,700		$ 1,700			$ 8,600
Aggregate estimated fair value of limited partnership units | $	$ 1,200		$ 1,200			$ 3,900
Number of outstanding limited partnership units, unvested (in shares)	100,000		100,000			100,000
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)	189,726	4,419	238,927	4,419
Class A Common Stock | Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Value of shares withheld | $	$ 1,400	$ 700	$ 7,600	$ 6,200
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	400,000,000