Summary of Significant Accounting Policies	6 Months Ended
Summary of Significant Accounting Policies	Jun. 30, 2015
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation The accompanying unaudited consolidated financial statements have been prepared by us in accordance with U.S. generally accepted accounting principles, or GAAP, pursuant to the rules and regulations of the Securities and Exchange Commission, or SEC, regarding interim financial reporting. Accordingly, the unaudited consolidated financial statements do not include all of the information and footnotes required by GAAP for complete financial statements and should be read in conjunction with our audited consolidated financial statements and related notes thereto for the year ended December 31, 2014. The accompanying unaudited consolidated financial statements reflect all adjustments that are, in our opinion, necessary for a fair presentation of results for the interim periods presented. These adjustments are of a normal recurring nature. Preparing financial statements requires us to make certain estimates and assumptions that affect the amounts that are reported in the consolidated financial statements and accompanying disclosures. Although these estimates are based on our best knowledge of current events and actions that we may undertake in the future, actual results may be different from these estimates. The results of operations for the six months and three months ended June 30, 2015 are not necessarily indicative of the results to be expected for any future period or the full fiscal year. The accompanying unaudited consolidated financial statements include the accounts of us and our wholly-owned and controlled subsidiaries. All intercompany balances and transactions between us and our wholly-owned and controlled subsidiaries have been eliminated in the consolidation. For those consolidated subsidiaries in which our ownership is less than 100% and for which we have control over the assets and liabilities and the management of the entity, the outside stockholders’ interests are shown as non-controlling interests. In instances where outside stockholders' hold an option to require us to repurchase the outside stockholders' interest, these interests are shown as redeemable non-controlling interests. As discussed in Note 12, we completed the initial public offering, or IPO, and sale of our wholly-owned subsidiary Euronext and completed the sales of our wholly-owned subsidiaries Wombat, NYFIX and Metabit during 2014, and have included the financial results of these companies in discontinued operations in the accompanying consolidated financial statements. New and Recently Adopted Accounting Pronouncements In April 2015, the Financial Accounting Standards Board issued Accounting Standards Update No. 2015-03, Simplifying the Presentation of Debt Issuance Costs, or ASU 2015-03. This standard amends the existing guidance to require that debt issuance costs be presented in the balance sheet as a deduction from the carrying amount of the related debt liability instead of as a deferred charge. ASU 2015-03 is effective on a retrospective basis for annual reporting periods beginning after December 15, 2015, but early adoption is permitted. We do not expect to adopt this amendment early, and the adoption is not expected to have a material effect on our consolidated financial statements. Reclassifications Certain prior period amounts have been reclassified to conform to the current period’s financial statement presentation.