Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2019	Nov. 05, 2019
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Entity Registrant Name	BGC Partners, Inc.
Entity Central Index Key	0001094831
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity File Number	0-28191
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
Entity Interactive Data Current	Yes
Entity Incorporation State Country Code	DE
Title of 12(b) Security	Class A Common Stock, $0.01 par value
Trading Symbol	BGCP
Security Exchange Name	NASDAQ
Document Quarterly Report	true
Document Transition Report	false
Class A Common Stock [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		302,760,326
Class B Common Stock [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		45,884,380