Compensation - Additional Information (Detail) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2022 USD ($) shares	Sep. 30, 2021 USD ($) shares	Sep. 30, 2022 USD ($) shares	Sep. 30, 2021 USD ($) shares	Dec. 31, 2021 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)	135,600,000		135,600,000
Number of share-equivalent limited partnership units exchangeable into shares (in shares)	1,400,000		1,400,000		1,300,000
Number of common stock settled per restricted stock unit (in shares)			1
Aggregate estimated fair value of limited partnership units and restricted stock units | $			$ 5,400		$ 8,900
Aggregate estimated fair value of deferred compensation awards | $			$ 21,900		$ 21,700
Shares, forfeited (in shares)	43,000	56,000	47,000	140,000
Number of shares released the restrictions (in shares)	100,000	600,000	200,000	1,100,000
Deferred cash compensation expense recognized | $			$ 75	$ 321
Deferred cash compensation expense not yet recognized | $	$ 100		$ 100
Deferred compensation expense, expected period of recognition			2 years 6 months 18 days
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to unvested | $	$ 43,600		$ 43,600
Unrecognized compensation expense related to unvested recognized period			2 years 7 months 9 days
Limited partnership units outstanding (in shares)	11,913,000		11,913,000		11,034,000
Restricted Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Limited partnership units outstanding (in shares)	2,400,000		2,400,000		2,600,000
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]
Common stock exchangeable basis			1
Limited partnership interests exchange ratio			0.9365
Unrecognized compensation expense related to unvested | $	$ 95,000		$ 95,000
Unrecognized compensation expense related to unvested recognized period			1 year 10 months 13 days
Limited partnership units outstanding (in shares)	109,503,000		109,503,000		112,115,000
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)	25,000	400,000	100,000	500,000
Number of outstanding restricted shares held (in shares)	1,100,000		1,100,000		1,200,000
Newmark | LPUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Limited partnership units outstanding (in shares)	10,273,000		10,273,000		11,051,000
Newmark | LPUs | REUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Notional value with post-termination pay-out amount | $	$ 600		$ 600		$ 800
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)	700,000		700,000		1,300,000
Notional value with post-termination pay-out amount | $	$ 9,200		$ 9,200		$ 12,400
Aggregate estimated fair value of limited partnership units | $	$ 4,700		$ 4,700		$ 7,400
Number of outstanding limited partnership units, unvested (in shares)	100,000		100,000		100,000
GFI Group Inc.
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred cash compensation expense recognized | $	$ 13	$ 32	$ 100	$ 300
Liability for deferred cash compensation awards | $	$ 700		$ 700		$ 800
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)	400,000		400,000		400,000
Shares, forfeited (in shares)	43,388	56,423	47,807	140,188
Class A Common Stock | Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Value of shares withheld | $	$ 200	$ 26	$ 6,400	$ 3,800
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)						500,000,000	400,000,000