Earnings Per Share - Schedule of Allocations of Earnings (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Earnings Per Share [Abstract]
Net income available to common stockholders	$ 70,924	$ 23,864	$ 20,137
Allocation of net income to limited partnership interests in BGC Holdings	164,221	21,188	33,067
Fully diluted earnings per share:
Net income available to common stockholders	70,924	23,864	20,137
Allocation of net income to limited partnership interests in BGC Holdings, net of tax	25,912	22,161
Interest expense on convertible notes, net of tax
Dividend equivalent expense on RSUs, net of tax	15	217
Net income for fully diluted shares	$ 96,851	$ 46,242	$ 20,137
Weighted-average shares:
Common stock outstanding	193,694	144,886	116,132
Limited partnership interests in BGC Holdings	70,432	134,935
Convertible notes
RSUs (Treasury stock method)	413	581
Other	809	407	382
Fully diluted weighted-average shares of common stock outstanding	265,348	280,809	116,514
Fully diluted earnings per share	$ 0.36	$ 0.16	$ 0.17