Customer Concentration - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2013 Customer	Dec. 31, 2012 Customer	Dec. 31, 2011 Customer
Risks And Uncertainties [Abstract]
Number of client accounted for total revenue	0	0	0
Total revenue, accounted for single client	More than 10%	More than 10%	More than 10%
Percentage of trading volumes by single client	12.50%	13.50%	14.60%
Percentage of outstanding shares owned by single client	9.00%