Legal Proceedings	3 Months Ended
Mar. 31, 2016
Legal Proceedings [Abstract]
Legal Proceedings	NOTE 14 — LEGAL PROCEEDINGS As of March 31, 2016, the end of the period covered by this report, the Company was subject to various legal proceedings and claims, as well as certain other legal proceedings and claims that have not been fully resolved and that have arisen in the ordinary course of business. For a description of each of these proceedings, please see Note 12 to our consolidated financial statements included in our Annual Report on Form 10-K for the year ended December 31, 2015. The Company reviews its legal proceedings and claims, regulatory reviews and inspections and other legal proceedings on an ongoing basis and follows appropriate accounting guidance when making accrual and disclosure decisions. The Company establishes accruals for those contingencies where the incurrence of a loss is probable and can be reasonably estimated, and we disclose the amount accrued and the amount of a reasonably possible loss in excess of the amount accrued, if such disclosure is necessary for our financial statements to not be misleading. The Company does not record liabilities when the likelihood that the liability has been incurred is probable, but the amount cannot be reasonably estimated, or when the liability is believed to be only reasonably possible or remote. The Company's assessment of whether a loss is reasonably possible or probable is based on its assessment of the ultimate outcome of the matter following all appeals. As of March 31, 2016, the Company does not believe that there is a reasonable possibility that any material loss exceeding the amounts already recognized for these reviews, inspections or other legal proceedings, if any, has been incurred. While the consequences of certain unresolved proceedings are not presently determinable, the outcome of any litigation is inherently uncertain and an adverse outcome from certain matters could have a material effect on our earnings in any given reporting period. However, in the opinion of management, the ultimate liability is not expected to have a material effect on our financial position, liquidity or capital resources. ISE -- QRM On November 12, 2012, CBOE brought suit against International Securities Exchange, LLC ("ISE") in the United States District Court for the Northern District of Illinois alleging that ISE infringed three of its patents (United States Patent Nos. 7,356,498; 7,980,457; and 8,266,044 (the "QRM patents")) related to quote risk monitor ("QRM") technology. CBOE had requested injunctive relief and monetary damages. On February 20, 2013, the court ruled that the case be transferred to the United States District Court for the Southern District of New York, and on October 31, 2013, the Court stayed the litigation pending resolution of Covered Business Method ("CBM") Patent Reviews at the United States Patent and Trademark Office ("USPTO"), which ISE requested. On March 4, 2014, the USPTO instituted CBM Patent Reviews on CBOE’s three QRM patents. On May 22, 2014, the USPTO instituted Inter Parties Review ("IPR") Proceedings, which ISE requested, on some but not all claims of two of CBOE’s QRM patents (United States Patent Nos. 7,356,498 and 7,980,457). On March 2, 2015, the USPTO ruled in the CBM proceedings, finding that the subject matter of the patents is not eligible for patent protection, and in the IPR proceedings, finding for CBOE that the claims were not invalidated by the asserted prior art. On April 30, 2015, ISE filed notice of its appeal of the IPR decisions, and on May 1, 2015, CBOE filed notice of its appeal of the CBM decisions. The appeals are being handled by the United States Court of Appeals for the Federal Circuit. On March 25, 2016, the Court of Appeals affirmed the USPTO’s decisions that the QRM patents were directed to ineligible subject matter and dismissed ISE’s appeal and vacated the USPTO’s IPR decisions. Lanier Litigation On May 23, 2014, Harold R. Lanier sued 14 securities exchanges, including CBOE, in the United States District Court for the Southern District of New York on behalf of himself and a putative class consisting of all persons in the United States who entered into contracts to receive market data through certain data plans at any time since May 19, 2008 to the present. The complaint alleged that the market data provided under the CQ Plan and CTA Plans was inferior to the data that the exchanges provided to those that directly receive other data from the exchanges, which the plaintiffs alleged is a breach of their “subscriber contracts” and a violation of the exchanges’ obligations under the CQ and CTA Plans. The plaintiffs sought monetary and injunctive relief. On May 30, 2014, Mr. Lanier filed two additional suits in the same Court, alleging substantially the same claims and requesting the same types of relief against the exchanges who participate in the UTP and the OPRA data plans. CBOE was a defendant in each of these suits, while C2 was only a defendant in the suit regarding the OPRA Plan. On April 28, 2015, the Court dismissed Lanier’s complaint with prejudice because it was preempted by the federal regulatory scheme and because the claims were precluded by the terms of the applicable subscriber agreements. Mr. Lanier appealed the orders dismissing each of his three cases and, on September 2, 2015, he filed his opening appellate briefs in those cases. The defendants’ response briefs were filed November 24, 2015 and briefing on the appeals has concluded. The oral arguments on the appeals were heard on March 3, 2016. ISE -- '707 On November 22, 2006, ISE filed an action in the United States District Court for the Southern District of New York claiming that CBOE's Hybrid trading system infringes ISE's U.S. Patent No. 6,618,707 (the "'707 patent"). On January 31, 2007, CBOE filed an action in federal court in the Northern District of Illinois seeking a declaratory judgment that the '707 patent was not infringed, not valid and/or not enforceable against CBOE. The New York case was transferred to the federal court in the Northern District of Illinois on August 9, 2007. On March 14, 2013, ISE conceded to an adverse judgment in this matter and asked that the federal court in the Northern District of Illinois enter judgment for CBOE. ISE appealed certain court rulings to the Federal Circuit Court of Appeals. The federal court in the Northern District of Illinois on January 14, 2014 issued an opinion and order awarding certain costs associated with the litigation to CBOE. On April 7, 2014, the Federal Circuit Court of Appeals issued a favorable opinion to CBOE. On March 31, 2016, the federal court in the Northern District of Illinois granted CBOE’s motion for attorney fees and expenses and CBOE subsequently supplemented such request on April 7, 2016.

NOTE 14 — LEGAL PROCEEDINGS

As of March 31, 2016, the end of the period covered by this report, the Company was subject to various legal proceedings and claims, as well as certain other legal proceedings and claims that have not been fully resolved and that have arisen in the ordinary course of business. For a description of each of these proceedings, please see Note 12 to our consolidated financial statements included in our Annual Report on Form 10-K for the year ended December 31, 2015.

The Company reviews its legal proceedings and claims, regulatory reviews and inspections and other legal proceedings on an ongoing basis and follows appropriate accounting guidance when making accrual and disclosure decisions. The Company establishes accruals for those contingencies where the incurrence of a loss is probable and can be reasonably estimated, and we disclose the amount accrued and the amount of a reasonably possible loss in excess of the amount accrued, if such disclosure is necessary for our financial statements to not be misleading. The Company does not record liabilities when the likelihood that the liability has been incurred is probable, but the amount cannot be reasonably estimated, or when the liability is believed to be only reasonably possible or remote. The Company's assessment of whether a loss is reasonably possible or probable is based on its assessment of the ultimate outcome of the matter following all appeals.

As of March 31, 2016, the Company does not believe that there is a reasonable possibility that any material loss exceeding the amounts already recognized for these reviews, inspections or other legal proceedings, if any, has been incurred. While the consequences of certain unresolved proceedings are not presently determinable, the outcome of any litigation is inherently uncertain and an adverse outcome from certain matters could have a material effect on our earnings in any given reporting period. However, in the opinion of management, the ultimate liability is not expected to have a material effect on our financial position, liquidity or capital resources.

ISE -- QRM

On November 12, 2012, CBOE brought suit against International Securities Exchange, LLC ("ISE") in the United States District Court for the Northern District of Illinois alleging that ISE infringed three of its patents (United States Patent Nos. 7,356,498; 7,980,457; and 8,266,044 (the "QRM patents")) related to quote risk monitor ("QRM") technology. CBOE had requested injunctive relief and monetary damages. On February 20, 2013, the court ruled that the case be transferred to the United States District Court for the Southern District of New York, and on October 31, 2013, the Court stayed the litigation pending resolution of Covered Business Method ("CBM") Patent Reviews at the United States Patent and Trademark Office ("USPTO"), which ISE requested. On March 4, 2014, the USPTO instituted CBM Patent Reviews on CBOE’s three QRM patents. On May 22, 2014, the USPTO instituted Inter Parties Review ("IPR") Proceedings, which ISE requested, on some but not all claims of two of CBOE’s QRM patents (United States Patent Nos. 7,356,498 and 7,980,457). On March 2, 2015, the USPTO ruled in the CBM proceedings, finding that the subject matter of the patents is not eligible for patent protection, and in the IPR proceedings, finding for CBOE that the claims were not invalidated by the asserted prior art. On April 30, 2015, ISE filed notice of its appeal of the IPR decisions, and on May 1, 2015, CBOE filed notice of its appeal of the CBM decisions. The appeals are being handled by the United States Court of Appeals for the Federal Circuit. On March 25, 2016, the Court of Appeals affirmed the USPTO’s decisions that the QRM patents were directed to ineligible subject matter and dismissed ISE’s appeal and vacated the USPTO’s IPR decisions.

Lanier Litigation

On May 23, 2014, Harold R. Lanier sued 14 securities exchanges, including CBOE, in the United States District Court for the Southern District of New York on behalf of himself and a putative class consisting of all persons in the United States who entered into contracts to receive market data through certain data plans at any time since May 19, 2008 to the present. The complaint alleged that the market data provided under the CQ Plan and CTA Plans was inferior to the data that the exchanges provided to those that directly receive other data from the exchanges, which the plaintiffs alleged is a breach of their “subscriber contracts” and a violation of the exchanges’ obligations under the CQ and CTA Plans. The plaintiffs sought monetary and injunctive relief. On May 30, 2014, Mr. Lanier filed two additional suits in the same Court, alleging substantially the same claims and requesting the same types of relief against the exchanges who participate in the UTP and the OPRA data plans. CBOE was a defendant in each of these suits, while C2 was only a defendant in the suit regarding the OPRA Plan. On April 28, 2015, the Court dismissed Lanier’s complaint with prejudice because it was preempted by the federal regulatory scheme and because the claims were precluded by the terms of the applicable subscriber agreements. Mr. Lanier appealed the orders dismissing each of his three cases and, on September 2, 2015, he filed his opening appellate briefs in those cases. The defendants’ response briefs were filed November 24, 2015 and briefing on the appeals has concluded. The oral arguments on the appeals were heard on March 3, 2016.

ISE -- '707

On November 22, 2006, ISE filed an action in the United States District Court for the Southern District of New York claiming that CBOE's Hybrid trading system infringes ISE's U.S. Patent No. 6,618,707 (the "'707 patent"). On January 31, 2007, CBOE filed an action in federal court in the Northern District of Illinois seeking a declaratory judgment that the '707 patent was not infringed, not valid and/or not enforceable against CBOE. The New York case was transferred to the federal court in the Northern District of Illinois on August 9, 2007.

On March 14, 2013, ISE conceded to an adverse judgment in this matter and asked that the federal court in the Northern District of Illinois enter judgment for CBOE. ISE appealed certain court rulings to the Federal Circuit Court of Appeals. The federal court in the Northern District of Illinois on January 14, 2014 issued an opinion and order awarding certain costs associated with the litigation to CBOE. On April 7, 2014, the Federal Circuit Court of Appeals issued a favorable opinion to CBOE. On March 31, 2016, the federal court in the Northern District of Illinois granted CBOE’s motion for attorney fees and expenses and CBOE subsequently supplemented such request on April 7, 2016.