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Sale of Building
6 Months Ended
Jun. 30, 2012
Sale of Building [Abstract]  
Property, Plant and Equipment Disclosure [Text Block]
Property
In April 2012, CME Group sold the north and south towers of the CBOT building for $151.5 million resulting in a gain of $20.3 million. At the time of the sale, the company leased back a portion of the property. As a result of the leaseback, the company is required to recognize the gain as a reduction to operating expenses over the 15 year term of the lease.