Legal Proceedings	3 Months Ended
Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Legal Proceedings	Legal Proceedings We are subject to legal proceedings, claims and investigations that arise in the ordinary course of our business. These include the matters described in Part I, Item 3 “Legal Proceedings” and Note 14 to the consolidated financial statements in Part II, Item 8 of our 2017 Form 10-K. We establish accruals for those matters in circumstances when a loss contingency is considered probable and the related amount is reasonably estimable. Any such accruals may be adjusted as circumstances change. Assessments of losses are inherently subjective and involve unpredictable factors. We do not believe that the resolution of these legal matters, including the matters described below, will have a material adverse effect on our consolidated financial condition, results of operations, or liquidity. It is possible, however, that future results of operations for any particular quarterly or annual period could be materially and adversely affected by any developments relating to the legal proceedings, claims and investigations. During the year ended December 31, 2017, we recorded an aggregate of $14 million in expense accruals relating to SEC investigations and inquiries. On March 6, 2018, NYSE and affiliated exchanges reached a settlement with the SEC of the various matters under investigation and agreed to pay a $14 million civil monetary penalty, together with certain non-monetary relief. For further details about the settlement and underlying matters that were under investigation, please refer to Order Instituting Administrative and Cease-and-Desist Proceedings Pursuant to Section 8A of the Securities Act of 1933, Sections 19(h)(1) and 21C of the Securities Exchange Act of 1934, Making Findings, and Imposing Remedial Sanctions and a Cease-and-Desist Order, Administrative Proceeding File No. 3-18388 (In the Matter of New York Stock Exchange LLC, NYSE American LLC, and NYSE Arca, Inc.) entered on March 6, 2018. Our 2017 Form 10-K included a description of the purported class action lawsuit against two of our subsidiary NYSE exchanges, and other U.S. exchanges, by the City of Providence, Rhode Island and other plaintiffs. As reported in our 2017 Form 10-K, the defendant exchanges filed a petition for rehearing and/or rehearing en banc of the Second Circuit’s December 2017 decision vacating the dismissal of this case, and on March 13, 2018, the Second Circuit denied our petition.

Legal Proceedings

We are subject to legal proceedings, claims and investigations that arise in the ordinary course of our business. These include the matters described in Part I, Item 3 “Legal Proceedings” and Note 14 to the consolidated financial statements in Part II, Item 8 of our 2017 Form 10-K. We establish accruals for those matters in circumstances when a loss contingency is considered probable and the related amount is reasonably estimable. Any such accruals may be adjusted as circumstances change. Assessments of losses are inherently subjective and involve unpredictable factors. We do not believe that the resolution of these legal matters, including the matters described below, will have a material adverse effect on our consolidated financial condition, results of operations, or liquidity. It is possible, however, that future results of operations for any particular quarterly or annual period could be materially and adversely affected by any developments relating to the legal proceedings, claims and investigations.

During the year ended December 31, 2017, we recorded an aggregate of $14 million in expense accruals relating to SEC investigations and inquiries. On March 6, 2018, NYSE and affiliated exchanges reached a settlement with the SEC of the various matters under investigation and agreed to pay a $14 million civil monetary penalty, together with certain non-monetary relief. For further details about the settlement and underlying matters that were under investigation, please refer to Order Instituting Administrative and Cease-and-Desist Proceedings Pursuant to Section 8A of the Securities Act of 1933, Sections 19(h)(1) and 21C of the Securities Exchange Act of 1934, Making Findings, and Imposing Remedial Sanctions and a Cease-and-Desist Order, Administrative Proceeding File No. 3-18388 (In the Matter of New York Stock Exchange LLC, NYSE American LLC, and NYSE Arca, Inc.) entered on March 6, 2018.

Our 2017 Form 10-K included a description of the purported class action lawsuit against two of our subsidiary NYSE exchanges, and other U.S. exchanges, by the City of Providence, Rhode Island and other plaintiffs. As reported in our 2017 Form 10-K, the defendant exchanges filed a petition for rehearing and/or rehearing en banc of the Second Circuit’s December 2017 decision vacating the dismissal of this case, and on March 13, 2018, the Second Circuit denied our petition.