Contingencies	9 Months Ended
Sep. 30, 2015
Loss Contingency [Abstract]
Contingencies	Contingencies Legal and Regulatory Matters. In 2008, Fifth Market, Inc. (Fifth Market) filed a complaint against CME Group and CME in the Delaware District Court seeking a permanent injunction against CME's Globex system and unquantified enhanced damages for what the plaintiff alleges is willful infringement of two patents, in addition to costs, expenses and attorneys' fees. The case was stayed pending the outcome of CME's request for reexamination by the U.S. Patent and Trademark Office (USPTO). The reexaminations resulted in some claims being rejected and others being confirmed. In June 2013, the court lifted the stay. The validity of the patents, however, remains subject to further review by the USPTO. CME filed covered business method reviews against both patents for the claims that remain after the reexaminations. All the claims asserted in the litigation have a proceeding instituted against them. The reviews and one reexamination remain under way at the USPTO or are on appeal to the Federal Circuit. 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 Fifth Market legal matter involves an alleged infringement of intellectual property which, due to its nature, involves a potential liability that is uncertain, difficult to quantify and involves a wide range of potential outcomes. We expect the re-examination and the reviews by the USPTO in the Fifth Market matter, including any appeals thereof, to result in a determination of the validity of the patent at issue which we expect will have an impact on the merits of the matter. Given the uncertainty of factors which may potentially impact the resolution of the matter, 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 at trial in the matter. In February 2013, the CFTC filed suit against NYMEX and two former employees alleging disclosure of confidential customer information in violation of the Commodity Exchange Act. NYMEX’s motion to dismiss was denied in September 2014. Based on its investigation to date and advice from legal counsel, the company believes that it has strong factual and legal defenses to the claim. In the normal course of business, the company discusses matters with its regulators raised during regulatory examinations or otherwise subject to their 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, 2015 and December 31, 2014, the company had accrued $3.5 million and $4.3 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 platforms; utilizing market data services, and licensing CME SPAN software may contain indemnifications from intellectual property claims that may be made against customers and other third parties 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 in the Delaware District Court seeking a permanent injunction against CME's Globex system and unquantified enhanced damages for what the plaintiff alleges is willful infringement of two patents, in addition to costs, expenses and attorneys' fees. The case was stayed pending the outcome of CME's request for reexamination by the U.S. Patent and Trademark Office (USPTO). The reexaminations resulted in some claims being rejected and others being confirmed. In June 2013, the court lifted the stay. The validity of the patents, however, remains subject to further review by the USPTO. CME filed covered business method reviews against both patents for the claims that remain after the reexaminations. All the claims asserted in the litigation have a proceeding instituted against them. The reviews and one reexamination remain under way at the USPTO or are on appeal to the Federal Circuit. 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 Fifth Market legal matter involves an alleged infringement of intellectual property which, due to its nature, involves a potential liability that is uncertain, difficult to quantify and involves a wide range of potential outcomes. We expect the re-examination and the reviews by the USPTO in the Fifth Market matter, including any appeals thereof, to result in a determination of the validity of the patent at issue which we expect will have an impact on the merits of the matter. Given the uncertainty of factors which may potentially impact the resolution of the matter, 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 at trial in the matter.

In February 2013, the CFTC filed suit against NYMEX and two former employees alleging disclosure of confidential customer information in violation of the Commodity Exchange Act. NYMEX’s motion to dismiss was denied in September 2014. Based on its investigation to date and advice from legal counsel, the company believes that it has strong factual and legal defenses to the claim.

In the normal course of business, the company discusses matters with its regulators raised during regulatory examinations or otherwise subject to their 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, 2015 and December 31, 2014, the company had accrued $3.5 million and $4.3 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 platforms; utilizing market data services, and licensing CME SPAN software may contain indemnifications from intellectual property claims that may be made against customers and other third parties 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.