Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2021	Feb. 24, 2022	Jun. 30, 2021
Document Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Transition Report	false
Entity File Number	0-28191
Entity Registrant Name	BGC Partners, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	13-4063515
Entity Address, Address Line One	499 Park Avenue
Entity Address, City or Town	New York
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	10022
City Area Code	212
Local Phone Number	610-2200
Title of 12(b) Security	Class A Common Stock, $0.01 par value
Trading Symbol	BGCP
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 1,929,824,116
Documents Incorporated by Reference	Portions of the registrant’s definitive proxy statement for its 2022 annual meeting of stockholders (the “2022 Proxy Statement”) are incorporated by reference in Part III of this Annual Report on Form 10-K. We anticipate that we will file the 2022 Proxy Statement with the SEC on or before May 2, 2022.
Amendment Flag	false
Document Period End Date	Dec. 31, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Entity Central Index Key	0001094831
Current Fiscal Year End Date	--12-31
Class A Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		321,093,235
Class B Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		45,884,380