Customer Concentration	9 Months Ended
Customer Concentration	Sep. 30, 2013
Risks And Uncertainties [Abstract]
Customer Concentration	14. Customer Concentration During both the nine months ended September 30, 2013 and 2012, no single client accounted for more than 10% of total revenue. One client accounted for 12.6% and 14.2% of trading volumes during the nine months ended September 30, 2013 and 2012, respectively.

The entire disclosure for any concentrations existing at the date of the financial statements that make an entity vulnerable to a reasonably possible, near-term, severe impact. This disclosure informs financial statement users about the general nature of the risk associated with the concentration, and may indicate the percentage of concentration risk as of the balance sheet date.

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