Condensed Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Total	Smith Mack	Class B Common Stock	Common Stock Class A Common Stock	Common Stock Class A Common Stock Smith Mack	Common Stock Class B Common Stock	Additional Paid-in Capital	Additional Paid-in Capital Smith Mack	Additional Paid-in Capital Class B Common Stock	Treasury Stock	Retained Deficit	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interest in Subsidiaries	Noncontrolling Interest in Subsidiaries Smith Mack	Noncontrolling Interest in Subsidiaries Class B Common Stock
Beginning balance at Dec. 31, 2021	$ 663,315			$ 4,359		$ 459	$ 2,451,135			$ (623,734)	$ (1,171,919)	$ (40,548)	$ 43,563
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Consolidated net income (loss)	55,269										46,496		8,773
Other comprehensive income (loss), net of tax	(14,763)											(12,535)	(2,228)
Equity-based compensation	11,964			30			9,081						2,853
Dividends to common stockholders and participating RSU holders	(11,143)										(11,143)
Earnings distributions to limited partnership interests and other noncontrolling interests	(2,950)												(2,950)
Grant of exchangeability and redemption of limited partnership interests	82,939			237			61,849						20,853
Issuance of common stock	3,632	$ 2,710		5	$ 12		3,616	$ 2,279					11	$ 419
Redemption of FPUs	(204)												(204)
Repurchase of Class A common stock	(79,295)									(66,747)			(12,548)
Forfeiture of Class A common stock	(188)						(6)			(152)			(30)
Contributions of capital to and from Cantor for equity-based compensation	(504)						(370)						(134)
Cantor purchase of Cantor units from BGC Holdings upon redemption of FPUs	947												947
Other	(385)						(385)
Ending balance at Sep. 30, 2022	$ 711,344			4,643		459	2,527,199			(690,633)	(1,136,566)	(53,083)	59,325
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per share of common stock (in dollars per share)	$ 0.03
Dividends declared and paid per share of common stock (in dollars per share)	$ 0.03
Beginning balance at Jun. 30, 2022	$ 730,693			4,518		459	2,499,393			(648,500)	(1,138,628)	(46,456)	59,907
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Consolidated net income (loss)	8,225										5,762		2,463
Other comprehensive income (loss), net of tax	(7,744)											(6,627)	(1,117)
Equity-based compensation	3,975			4			3,034						937
Dividends to common stockholders and participating RSU holders	(3,700)										(3,700)
Earnings distributions to limited partnership interests and other noncontrolling interests	(3,091)												(3,091)
Grant of exchangeability and redemption of limited partnership interests	32,174			120			24,026						8,028
Issuance of common stock	154			1			149						4
Redemption of FPUs	(59)												(59)
Repurchase of Class A common stock	(49,908)									(41,994)			(7,914)
Forfeiture of Class A common stock	(171)						(5)			(139)			(27)
Contributions of capital to and from Cantor for equity-based compensation	818						624						194
Other	(22)						(22)
Ending balance at Sep. 30, 2022	$ 711,344			4,643		459	2,527,199			(690,633)	(1,136,566)	(53,083)	59,325
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per share of common stock (in dollars per share)	$ 0.01
Dividends declared and paid per share of common stock (in dollars per share)	$ 0.01
Beginning balance at Dec. 31, 2022	$ 733,208			4,719		459	2,559,418			(711,454)	(1,138,066)	(45,431)	63,563
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Consolidated net income (loss)	17,512										16,320		1,192
Other comprehensive income (loss), net of tax	129											(388)	517
Equity-based compensation	67,789			78			65,932			13			1,766
Dividends to common stockholders and participating RSU holders	(12,458)										(12,458)
Earnings distributions to limited partnership interests and other noncontrolling interests	(12,294)												(12,294)
Grant of exchangeability and redemption of limited partnership interests	113,201	$ 7,275		291	$ 55		86,505	$ 6,843					26,405	$ 377
Issuance of common stock	527			2			511						14
Redemption of FPUs	(547)												(547)
Repurchase of Class A common stock	(88,147)									(81,456)			(6,691)
Forfeiture of Class A common stock	(796)						84			(769)			(111)
Contributions of capital to and from Cantor for equity-based compensation	2,437						2,321						116
Cantor purchase of Cantor units from BGC Holdings upon redemption of FPUs	11,539												11,539
Redemption of FPUs and issuance of RSUs due to the Corporate Conversion	14,506						12,410						2,096
Cantor units converted into shares of BGC Group Class B common stock due to the Corporate Conversion, 63,974,374 shares			$ 0			640			$ 75,788						$ (76,428)
Restricted stock awards granted upon conversion of limited partnership interests due to the Corporate Conversion, 38,610,233 shares	0			386			(386)
Conversion of Class B Common Stock to Class A Common Stock, 405,801 shares	0			4		(4)
Cancellation of BGC Partners Inc. Treasury Stock due to Corporate Conversion, 156,386,616 shares	0			(1,563)			(751,768)			753,331
Other	1,778						1,778
Ending balance at Sep. 30, 2023	$ 855,659			3,972		1,095	2,059,436			(40,335)	(1,134,204)	(45,819)	11,514
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per share of common stock (in dollars per share)	$ 0.03
Dividends declared and paid per share of common stock (in dollars per share)	$ 0.03
Beginning balance at Jun. 30, 2023	$ 819,147			5,086		459	2,667,812			(753,331)	(1,146,350)	(41,128)	86,599
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Consolidated net income (loss)	18,552										17,046		1,506
Other comprehensive income (loss), net of tax	(4,854)											(4,691)	(163)
Equity-based compensation	60,256			55			60,191			10
Dividends to common stockholders and participating RSU holders	(4,900)										(4,900)
Issuance of common stock	170						170
Repurchase of Class A common stock	(40,345)									(40,345)
Contributions of capital to and from Cantor for equity-based compensation	1,931						1,931
Issuance of Class A common stock and RSUs for acquisitions, 413,884 shares	4,514			4			4,510
Cantor units converted into shares of BGC Group Class B common stock due to the Corporate Conversion, 63,974,374 shares			$ 0			640			$ 75,788						$ (76,428)
Restricted stock awards granted upon conversion of limited partnership interests due to the Corporate Conversion, 38,610,233 shares	0			386			(386)
Conversion of Class B Common Stock to Class A Common Stock, 405,801 shares	0			4		(4)
Cancellation of BGC Partners Inc. Treasury Stock due to Corporate Conversion, 156,386,616 shares	0			(1,563)			(751,768)			753,331
Other	1,188						1,188
Ending balance at Sep. 30, 2023	$ 855,659			$ 3,972		$ 1,095	$ 2,059,436			$ (40,335)	$ (1,134,204)	$ (45,819)	$ 11,514
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per share of common stock (in dollars per share)	$ 0.01
Dividends declared and paid per share of common stock (in dollars per share)	$ 0.01