Related Party Transactions - Additional Information (Detail) (USD $)	0 Months Ended	12 Months Ended					12 Months Ended			12 Months Ended							12 Months Ended				12 Months Ended	3 Months Ended	12 Months Ended		1 Months Ended	12 Months Ended	0 Months Ended	12 Months Ended				12 Months Ended					3 Months Ended	12 Months Ended	3 Months Ended		12 Months Ended				12 Months Ended												12 Months Ended
	Oct. 31, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Aug. 31, 2013	May 04, 2012	Dec. 31, 2013 ELX [Member]	Dec. 31, 2012 ELX [Member]	Mar. 28, 2012 ELX [Member]	Dec. 31, 2013 Cantor and ELX [Member]	Dec. 31, 2012 Cantor and ELX [Member]	Dec. 31, 2011 Cantor and ELX [Member]	Dec. 31, 2013 Cantor [Member]	Dec. 31, 2012 Cantor [Member]	Dec. 31, 2011 Cantor [Member]	Mar. 31, 2010 Cantor [Member]	Dec. 31, 2013 Class A Common Stock [Member]	Dec. 31, 2012 Class A Common Stock [Member]	Dec. 31, 2011 Class A Common Stock [Member] Partner	Jul. 27, 2011 Class A Common Stock [Member]	Dec. 31, 2013 Underwriting Fees [Member]	Jun. 30, 2013 Global Partnership Restructuring Program [Member]	Dec. 31, 2013 Global Partnership Restructuring Program [Member]	Jun. 30, 2013 Global Partnership Restructuring Program [Member] Class A Common Stock [Member]	Mar. 31, 2010 Senior Notes [Member]	Dec. 31, 2013 Senior Notes [Member]	Apr. 01, 2010 8.75% Convertible Notes [Member]	Dec. 31, 2013 8.75% Convertible Notes [Member]	Dec. 31, 2012 8.75% Convertible Notes [Member]	Dec. 31, 2011 8.75% Convertible Notes [Member]	Mar. 31, 2010 8.75% Convertible Notes [Member]	Dec. 31, 2013 Service Agreements [Member]	Dec. 31, 2012 Service Agreements [Member]	Dec. 31, 2011 Service Agreements [Member]	Dec. 31, 2013 CO2e [Member]	Aug. 09, 2011 CO2e [Member]	Jun. 30, 2013 Executive Officers [Member]	Dec. 31, 2011 Executive Officers [Member] Class A Common Stock [Member]	Jun. 30, 2013 Executive Officers [Member] Global Partnership Restructuring Program [Member]	Jun. 30, 2013 Executive Officers [Member] Global Partnership Restructuring Program [Member] Class A Common Stock [Member]	Dec. 31, 2013 Charity Day [Member] Class A Common Stock [Member]	Dec. 31, 2012 Charity Day [Member] Class A Common Stock [Member]	Dec. 31, 2013 Cantor and Freedom International Brokerage [Member]	Dec. 31, 2012 Cantor and Freedom International Brokerage [Member]	Dec. 31, 2013 Employee Loans [Member]	Dec. 31, 2012 Employee Loans [Member]	Dec. 31, 2011 Employee Loans [Member]	Dec. 31, 2013 Controlled Equity Offerings [Member]	Dec. 31, 2012 Controlled Equity Offerings [Member]	Dec. 31, 2011 Controlled Equity Offerings [Member]	Dec. 31, 2012 Cantor Rights to Purchase Exchangeable Units [Member]	Dec. 31, 2013 Stephen M. Merkel [Member] Class A Common Stock [Member]	Dec. 31, 2013 Shaun D. Lynn [Member] Class A Common Stock [Member]	Dec. 31, 2013 Aqua [Member]	Dec. 31, 2012 Aqua [Member]	Dec. 31, 2013 Aqua [Member] Cantor [Member]	Dec. 31, 2011 Cantor Exchanges [Member]	Dec. 31, 2013 Cantor Exchanges [Member]
Related Party Transaction [Abstract]
Mark-up cost of services																																7.50%
Company ownership of Tower Bridge																																52.00%
Cantor ownership of Tower Bridge																																48.00%
Equity investment in ELX		$ 1,748,000	$ 17,501,000	$ 1,749,000			$ 0	$ 16,000,000																																														$ 1,700,000	$ 1,600,000
Credit agreement commitment to variable interest entity							16,000,000		16,000,000
Credit facility commitment period							Mar. 28, 2015
Amount Loaned under credit agreement to ELX							0
Recognized related party revenues		41,128,000	53,159,000	62,227,000						41,100,000	53,200,000	62,200,000
Service charges																																32,700,000	35,300,000	36,800,000
Compensation to leased employees																																23,300,000	23,500,000	25,200,000
Cantor's share of net profit in Tower Bridge																																100,000	2,100,000	2,600,000
Interest income related to reverse repurchase agreements													68,000	0	0
Reverse repurchase agreements													0	0
Recognition of share of foreign exchange gain (loss)		(346,000)	47,000	(1,800,000)
Investment in asset-backed commercial paper program		250,000,000
Investment authorization in asset-backed commercial paper program					350,000,000
Receivables from Freedom International Brokerage																																											2,600,000	2,900,000
Receivables from Cantor related to open derivative contracts																																											500,000	0
Payables to Cantor related to open derivative contracts																																											900,000	300,000
Common stock																	1,053,842	4,797,177	3,829,176			44,000,000																		3,553,345
Common stock issued, restricted shares																						41,000,000	41,000,000																3,561,392
Recognized reserve		160,500,000
Employee loans		142,769,000	220,098,000																																										142,800,000	220,100,000
Compensation expense related to employee loans																																													195,000,000	35,600,000	31,800,000
Principal amount of notes																150,000,000											150,000,000	150,000,000	150,000,000		150,000,000
Repayment of Senior Notes																									150,000,000
Debt instrument maturity year																											2015
Convertible Notes issuance date																										Apr. 01, 2010
Interest expense																												13,100,000	13,100,000	13,200,000
Stated interest rate																											8.75%	8.75%	8.75%		8.75%
Related party expenses related to the Company's controlled equity offerings																																																900,000	1,700,000	1,400,000
Advisory fee			1,000,000	1,400,000
Fee paid related to divestiture		7,400,000
Debt issuance costs																					200,000
Related party service fee	10.00%
Professional and consulting fees	300,000	51,384,000	72,777,000	67,746,000
Related party revenue		1,500,000	1,100,000
Number of non-exchangeable FPUs redeemed		1,802,608																																																	431,985
Consideration for non-exchangeable FPUs redeemed																																																			1,282,045
Limited partnership units purchased																																																			431,985
FPUs remaining for which Cantor has the right to purchase Cantor units																																																			488,744
Aggregate consideration paid in connection with the grant of exchangeability and exchange of FPUs														1,449,663
Limited partnership units Exchange ratio			1
Exchangeable FPUs			488,744
Non-exchangeable FPUs remaining		2,669,952
Date of acquisition																																			Aug. 09, 2011
Liabilities assumed in a business acquisition																																				2,000,000
Number of partnership units issued to executive officer						2,449,312
Options exercised by Chief Executive Officer																																						1,500,000
Exercise price of options exercised by Chief Executive Officer																																						$ 5.10
Options exercised by other executive officers				2,047,249																																		152,188
Class A common stock repurchased from executive officers																			60,929																			6,454														33,478	533,406
Exercise price of options exercised by executive officers																																						$ 5.10
Average price per share of common stock repurchased from executive officers																																						$ 8.50														$ 5.61	$ 5.82
Average price per share of common stock repurchased		$ 5.09															$ 5.09	$ 7.66	$ 6.43
Repurchase of Class A common stock		3,046,857															3,046,857	44,013	60,929
Redemption/exchange of limited partnership units																						76,000,000	76,000,000																9,930,675
Shares withheld for taxes																																					1,028,128
Limited partnership units issued, as a percentage of non-exchangeable units redeemed		9.75%
Partnership units received by related parties		283,206
Shares issued and donated to Relief Fund by company																			443,686																						1,000,000	2,860,000
Charitable contributions		25,000,000
Number of partners donating common stock to the Relief Fund																			3
Donations of Class A common stock to the Relief Fund by partners																			995,911
Aggregate Class A common stock issued																	202,671,000	141,955,000		995,911				44,000,000
Authorization amount for loans and investments																																																						11,600,000
Ownership percentage							49.00%																																															49.00%		51.00%
Principal sum of loan due from related parties		$ 15,211,000	$ 21,655,000																																																			$ 980,000
Maturity date of subordinated loan																																																						Sep. 01, 2015
Loan Receivable, Description of Variable Rate Basis																																																						Three month LIBOR plus 600 basis points
Loan Receivable, Basis Spread on Variable Rate																																																						6.00%
Class A common shares issued to Cantor in exchange for units																																																									9,000,000
Class B common shares issued to Cantor in exchange for units																																																									9,000,000
Cantor units																																																									18,000,000
Cantor units held by Cantor																																																										48,782,933