Contingencies	9 Months Ended
Sep. 30, 2012
Loss Contingency [Abstract]
Contingencies	Contingencies Legal and Regulatory Matters. In 2008, Fifth Market, Inc. (Fifth Market) filed a complaint against CME Group and CME seeking a permanent injunction against CME's Globex system and unquantified enhanced damages for what the plaintiff alleges is willful infringement of two U.S. patents, in addition to costs, expenses and attorneys' fees. In March 2012, the U.S. Patent and Trademark Office (USPTO) issued an Office Action that rejected all of the claims in the first patent in a reexamination proceeding. Fifth Market replied to the rejection and may appeal the decision from the USPTO. CME initiated a second reexamination against the second asserted patent. The USPTO confirmed some claims and rejected others. Based on its investigation to date and advice from legal counsel, the company believes this suit is without merit and intends to defend itself vigorously against these charges. In 2009, CME and CBOT filed a complaint against Howard Garber seeking a declaratory judgment that neither CME nor CBOT infringed Mr. Garber's patent and that his patent is invalid and unenforceable. The case is stayed pending the outcome of the reexamination of his patent at the USPTO. In response to CME's reexamination request, the USPTO issued a Final Office Action that rejected all of the claims in the patent in October 2012. Mr. Garber may appeal this decision with the Board of Patent Appeals and Interferences. Based on its investigation to date and advice from legal counsel, the company believes this suit is without merit and intends to defend itself vigorously against these charges. In 2009, Realtime Data LLC (Realtime) filed a complaint against CME Group and other exchanges alleging willful infringement of four patents which was later amended to add CBOT and NYMEX as defendants. Subsequently, two additional lawsuits have been filed each adding a claim for the infringement of an additional patent. Both of these lawsuits have been consolidated with the original action. Realtime is seeking a permanent injunction, enhanced damages, attorneys' fees and costs. Three of the six asserted patents in this case have been dismissed due in part to the rejections of the patents in the reexaminations by the USPTO. In July 2012, the USPTO rejected all the claims in a fourth of the six patents. In September 2012, the federal court in the Southern District of New York ruled in the company's favor on a number of grounds of non-infringement relating to the Realtime Data patents. We expect that Realtime Data will appeal this decision. The USPTO will continue to review the patents in parallel. Based on its investigation to date and advice from legal counsel, the company believes this suit is without merit and intends to defend itself vigorously against these charges. The foregoing legal matters involve alleged infringements of intellectual property, which due to their nature involve potential liability that is uncertain, difficult to quantify and involve a wide range of potential outcomes. The company believes that the matters are without merit and intends to defend itself vigorously against the claims. The USPTO's determination of validity of the patents in the Fifth Market, Realtime, and Garber matters may have an impact on the merits of the cases. A number of lawsuits were filed in federal court in New York on behalf of all commodity account holders or customers of MF Global who had not received a return of 100% of their funds. These matters have been consolidated into a single action in federal court in New York, and a consolidated amended class action complaint was filed on November 5, 2012. The class action complaint alleges that CME violated the Commodity Exchange Act (CEA), aided and abetted violations of the CEA by other defendants, and aided and abetted a breach of fiduciary duty by certain officers and directors of MF Global. The class complaint also alleges that CME Group aided and abetted CME's violation of the CEA. The complaint does not allege the amount of damages sought, but rather seeks compensatory and exemplary damages to be determined at trial. Based on the initial analysis of the class complaint, the company believes that they have strong legal and factual defenses to the claims. In addition to the class complaint, the company is aware of two plaintiffs who intend to pursue their claims individually. Given that these matters are in the very early stage, at this time the company is unable to estimate the reasonably possible loss or range of reasonably possible loss in the unlikely event it were found to be liable in these matters. In the normal course of business, the company discusses matters with its regulators that either arise during regulatory examinations or are otherwise subject to the regulator's inquiry and oversight. These matters could result in censures, fines, penalties or other sanctions. Management believes the outcome of any resulting actions will not have a material impact on its consolidated financial position or results of operations. However, the company is unable to predict the outcome or the timing of the ultimate resolution of these matters, or the potential fines, penalties or injunctive or other equitable relief, if any, that may result from these matters. In addition, the company is a defendant in, and has potential for, various other legal proceedings arising from its regular business activities. While the ultimate results of such proceedings against the company cannot be predicted with certainty, the company believes that the resolution of any of these matters on an individual basis will not have a material impact on its consolidated financial position or results of operations. At September 30, 2012 and December 31, 2011, the company had accrued $13.3 million and $12.8 million, respectively, for legal and regulatory matters that were probable and estimable. Intellectual Property Indemnifications. Certain agreements with customers and other third parties related to accessing the CME Globex platform, the CME ClearPort platform, and/or the Clearing 21 platform; utilizing market data services; licensing CME SPAN software; and calculating indexes as a service provider and licensing indexes as the basis of financial products may contain indemnifications from intellectual property claims that may be made against them as a result of their use of the applicable products and/or services. The potential future claims relating to these indemnifications cannot be estimated and, therefore, no liability has been recorded.

Contingencies

Legal and Regulatory Matters. In 2008, Fifth Market, Inc. (Fifth Market) filed a complaint against CME Group and CME seeking a permanent injunction against CME's Globex system and unquantified enhanced damages for what the plaintiff alleges is willful infringement of two U.S. patents, in addition to costs, expenses and attorneys' fees. In March 2012, the U.S. Patent and Trademark Office (USPTO) issued an Office Action that rejected all of the claims in the first patent in a reexamination proceeding. Fifth Market replied to the rejection and may appeal the decision from the USPTO. CME initiated a second reexamination against the second asserted patent. The USPTO confirmed some claims and rejected others. Based on its investigation to date and advice from legal counsel, the company believes this suit is without merit and intends to defend itself vigorously against these charges.

In 2009, CME and CBOT filed a complaint against Howard Garber seeking a declaratory judgment that neither CME nor CBOT infringed Mr. Garber's patent and that his patent is invalid and unenforceable. The case is stayed pending the outcome of the reexamination of his patent at the USPTO. In response to CME's reexamination request, the USPTO issued a Final Office Action that rejected all of the claims in the patent in October 2012. Mr. Garber may appeal this decision with the Board of Patent Appeals and Interferences. Based on its investigation to date and advice from legal counsel, the company believes this suit is without merit and intends to defend itself vigorously against these charges.

In 2009, Realtime Data LLC (Realtime) filed a complaint against CME Group and other exchanges alleging willful infringement of four patents which was later amended to add CBOT and NYMEX as defendants. Subsequently, two additional lawsuits have been filed each adding a claim for the infringement of an additional patent. Both of these lawsuits have been consolidated with the original action. Realtime is seeking a permanent injunction, enhanced damages, attorneys' fees and costs. Three of the six asserted patents in this case have been dismissed due in part to the rejections of the patents in the reexaminations by the USPTO. In July 2012, the USPTO rejected all the claims in a fourth of the six patents. In September 2012, the federal court in the Southern District of New York ruled in the company's favor on a number of grounds of non-infringement relating to the Realtime Data patents. We expect that Realtime Data will appeal this decision. The USPTO will continue to review the patents in parallel. Based on its investigation to date and advice from legal counsel, the company believes this suit is without merit and intends to defend itself vigorously against these charges.

The foregoing legal matters involve alleged infringements of intellectual property, which due to their nature involve potential liability that is uncertain, difficult to quantify and involve a wide range of potential outcomes. The company believes that the matters are without merit and intends to defend itself vigorously against the claims. The USPTO's determination of validity of the patents in the Fifth Market, Realtime, and Garber matters may have an impact on the merits of the cases.

A number of lawsuits were filed in federal court in New York on behalf of all commodity account holders or customers of MF Global who had not received a return of 100% of their funds. These matters have been consolidated into a single action in federal court in New York, and a consolidated amended class action complaint was filed on November 5, 2012. The class action complaint alleges that CME violated the Commodity Exchange Act (CEA), aided and abetted violations of the CEA by other defendants, and aided and abetted a breach of fiduciary duty by certain officers and directors of MF Global. The class complaint also alleges that CME Group aided and abetted CME's violation of the CEA. The complaint does not allege the amount of damages sought, but rather seeks compensatory and exemplary damages to be determined at trial. Based on the initial analysis of the class complaint, the company believes that they have strong legal and factual defenses to the claims. In addition to the class complaint, the company is aware of two plaintiffs who intend to pursue their claims individually. Given that these matters are in the very early stage, at this time the company is unable to estimate the reasonably possible loss or range of reasonably possible loss in the unlikely event it were found to be liable in these matters.

In the normal course of business, the company discusses matters with its regulators that either arise during regulatory examinations or are otherwise subject to the regulator's inquiry and oversight. These matters could result in censures, fines, penalties or other sanctions. Management believes the outcome of any resulting actions will not have a material impact on its consolidated financial position or results of operations. However, the company is unable to predict the outcome or the timing of the ultimate resolution of these matters, or the potential fines, penalties or injunctive or other equitable relief, if any, that may result from these matters.

In addition, the company is a defendant in, and has potential for, various other legal proceedings arising from its regular business activities. While the ultimate results of such proceedings against the company cannot be predicted with certainty, the company believes that the resolution of any of these matters on an individual basis will not have a material impact on its consolidated financial position or results of operations. At September 30, 2012 and December 31, 2011, the company had accrued $13.3 million and $12.8 million, respectively, for legal and regulatory matters that were probable and estimable.

Intellectual Property Indemnifications. Certain agreements with customers and other third parties related to accessing the CME Globex platform, the CME ClearPort platform, and/or the Clearing 21 platform; utilizing market data services; licensing CME SPAN software; and calculating indexes as a service provider and licensing indexes as the basis of financial products may contain indemnifications from intellectual property claims that may be made against them as a result of their use of the applicable products and/or services. The potential future claims relating to these indemnifications cannot be estimated and, therefore, no liability has been recorded.