XML 30 R19.htm IDEA: XBRL DOCUMENT

Customer Concentration	6 Months Ended
Customer Concentration	Jun. 30, 2018
Risks And Uncertainties [Abstract]
Customer Concentration	11. Customer Concentration During both the six months ended June 30, 2018 and 2017, no single client accounted for more than 10% of total revenue. One institutional investor client accounted for 10.4% and 13.2% of trading volumes during the six months ended June 30, 2018 and 2017, respectively.