Consolidated Statements of Changes in Equity (Parenthetical)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Repurchase of Class A common stock, shares	3,046,857
Class A Common Stock [Member]
Equity-based compensation, shares	909,407	1,343,894	1,937,093
Grant of exchangeability and redemption of limited partnership interests, shares	55,953,246	18,024,094	12,259,184
Issuance of Class A common stock (net of costs), shares	1,053,842	4,797,177	3,829,176
Issuance of Class A common stock upon purchase of notes receivable, shares		453,172
Issuance of common stock upon exchange of Cantor units, shares			9,000,000
Repurchase of Class A common stock, shares	3,046,857	44,013	60,929
Issuance of contingent and Class A common stock for acquisitions, shares	2,799,604	2,119,393	4,716,848
Class B Common Stock [Member]
Issuance of common stock upon exchange of Cantor units, shares			9,000,000
Partnership Units [Member]
Redemption of founding/working partner units		1,928,069	236,741
Cantor purchase of Cantor units from BGC Holdings upon redemption of founding/working partner units		920,729
Partnership Units [Member] | Class A Common Stock [Member]
Redemption of founding/working partner units	1,373,065