Investments in and Advances to Affiliates | At September 30, 2015 and December 31, 2014 , the investments in affiliates were composed of the following (in thousands): September 30, December 31, Investment in OCC (1) $ 30,333 $ 333 Investment in Signal Trading Systems, LLC 12,444 11,900 Investment in IPXI Holdings, LLC (2) — 118 Cost method investments (3) 903 — Investment in CBOE Stock Exchange, LLC (4) — — Investments in Affiliates $ 43,680 $ 12,351 (1) In December 2014, OCC announced a newly-formed capital plan. The OCC capital plan was designed to strengthen OCC's capital base and facilitate its compliance with proposed SEC regulations for Systemically Important Financial Market Utilities ("SIFMUs") as well as international standards applicable to financial market infrastructures. On February 26, 2015, the SEC issued a notice of no objection to OCC's advance notice filing regarding the capital plan, and OCC and OCC’s existing exchange stockholders, which include CBOE, subsequently executed agreements effecting the capital plan. Under the plan, each of OCC's existing exchange stockholders agreed to contribute its pro-rata share, based on ownership percentage, of $150 million in equity capital, which would increase OCC's shareholders' equity, and to provide its pro rata share in replenishment capital, up to a maximum of $40 million per exchange stockholder, if certain capital thresholds are breached. OCC also adopted policies under the plan with respect to fees, customer refunds, and stockholder dividends, which envision an annual dividend payment to the exchange stockholders equal to the portion of OCC’s after-tax income that exceeds OCC’s capital requirements after payment of refunds to OCC’s clearing members (with such customer refunds generally to constitute 50% of the portion of OCC’s pre-tax income that exceeds OCC’s capital requirements). On March 3, 2015, in accordance with the plan, CBOE contributed $30.0 million to OCC. On March 6, 2015, OCC informed CBOE that the SEC had approved OCC's proposed rule filing for the capital plan. The SEC approval order was stayed on March 13, 2015 automatically as a result of the initiation of petitions to review the order. On September 10, 2015, the SEC issued orders that discontinued the automatic stay of the approval order and granted the petitions for the SEC to review the approval order. The SEC proceeding to review the approval order remains pending. If the SEC does not uphold the approval order, OCC will return each exchange stockholder’s capital contribution with interest. The contribution has been recorded under investments in affiliates in the balance sheet at September 30, 2015 . (2) IPXI Holdings, LLC ceased operations on March 23, 2015. (3) In September 2015, CBOE Holdings, through its subsidiary Loan Markets, LLC, acquired a minority interest in American Financial Exchange (AFX), an electronic marketplace for small and mid-sized banks to lend and borrow short-term funds. (4) CBOE Stock Exchange, LLC ceased trading operations on April 30, 2014. |