Income Tax Disclosure [Abstract] Income Taxes Income Tax Disclosure [Text Block] Goodwill and Intangible Assets Disclosure [Abstract] Components of intangible assets Intangible Assets Disclosure [Text Block] Future estimated amortization expense Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Goodwill activity Schedule of Goodwill [Table Text Block] Effective tax rate Effective Income Tax Rate, Continuing Operations Effective tax rate decrease due to a tax benefit Effective Income Tax Rate Reconciliation State Apportionment Effective Income Tax Rate Reconciliation State Apportionment Income tax benefit Income Tax Reconciliation State Apportionment Income Tax Reconciliation State Apportionment Decrease in effective tax rate due to valuation allowances Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance Reduction in valuation allowances Income Tax Reconciliation, Change in Deferred Tax Assets Valuation Allowance Valuation allowance Valuation Allowance, Amount Statement of Financial Position [Abstract] Statement [Table] Statement [Table] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] Preferred Stock [Member] Preferred Stock [Member] Series A Junior Participating Preferred Stock [Member] Series A Preferred Stock [Member] Class A Common Stock [Member] Common Class A [Member] Class B Common Stock [Member] Common Class B [Member] Statement [Line Items] Statement [Line Items] Accounts receivable, allowance Allowance for Doubtful Accounts Receivable, Current Restricted cash, current Restricted Cash and Cash Equivalents, Current Accumulated depreciation and amortization, property Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Restricted cash, noncurrent Restricted Cash and Cash Equivalents, Noncurrent Preferred stock, par value (in dollars per share) Preferred Stock, Par or Stated Value Per Share Preferred stock, shares authorized (in shares) Preferred Stock, Shares Authorized Preferred stock, shares issued (in shares) Preferred Stock, Shares Issued Preferred stock, shares outstanding (in shares) Preferred Stock, Shares Outstanding Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Common stock, shares authorized (in shares) Common Stock, Shares Authorized Common stock, shares issued (in shares) Common Stock, Shares, Issued Common stock, shares outstanding (in shares) Common Stock, Shares, Outstanding Business Transactions [Abstract] Business Transactions [Abstract] Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table] Equity Interest Issued or Issuable by Type [Axis] Equity Interest Issued or Issuable by Type [Axis] Equity Interest Issued or Issuable, Type [Domain] Equity Interest Issued or Issuable, Type [Domain] CME Group net of non-controlling interest [Member] CME Group net of non-controlling interest [Member] CME Group net of non-controlling interest [Member] Total CME Group [Member] Total CME Group [Member] Total CME Group [Member] CME Group [Member] CME Group [Member] CME Group [Member] Index Service [Member] Index Service [Member] Index Service [Member] Dow Jones [Member] Dow Jones [Member] Dow Jones Index Services [Member] Index Services [Member] Index Services [Member] Business Acquisition [Axis] Business Acquisition [Axis] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] Business Acquisition [Line Items] Business Acquisition [Line Items] Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners Gain on contribution of Dow Jones Index Asset Group Gain on contribution of assets Gain on contribution of assets Proceeds from Divestiture of Businesses Proceeds from Divestiture of Businesses Investment Owned, at Fair Value Investment Owned, at Fair Value Valuation model discount rate Valuation model discount rate Valuation model discount rate Loss on sale of Credit Market Analysis Ltd. Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal Reclassification adjustment for loss included in net income Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment Realized upon Sale or Liquidation, before Tax Statement of Cash Flows [Abstract] Statement, Scenario [Axis] Statement, Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Cash Flows from Operating Activities Net Cash Provided by (Used in) Operating Activities [Abstract] Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Adjustments to reconcile net income to net cash provided by operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Stock-based compensation Share-based Compensation Amortization of purchased intangibles Amortization of Intangible Assets Depreciation and amortization Depreciation, Depletion and Amortization, Nonproduction Amortization of debt financing costs and discount accretion Amortization of Financing Costs and Discounts Gain on sale of Index Services assets Gain (Loss) on Sale of Other Assets Gain on contribution of Dow Jones Index Asset Group Equity in net losses of unconsolidated subsidiaries Income (Loss) from Equity Method Investments Deferred income taxes Deferred Income Tax Expense (Benefit) Change in: Increase (Decrease) in Operating Capital [Abstract] Accounts receivable Increase (Decrease) in Accounts Receivable Other current assets Increase (Decrease) in Prepaid Expense and Other Assets Other assets Increase (Decrease) in Other Operating Assets Accounts payable Increase (Decrease) in Accounts Payable Income taxes payable Increase (Decrease) in Income Taxes Payable Other current liabilities Increase (Decrease) in Other Accrued Liabilities Other liabilities Increase (Decrease) in Other Operating Liabilities Other Other Noncash Income (Expense) Net Cash Provided by Operating Activities Net Cash Provided by (Used in) Operating Activities Cash Flows from Investing Activities Net Cash Provided by (Used in) Investing Activities [Abstract] Proceeds from maturities of available-for-sale marketable securities Proceeds from Maturities, Prepayments and Calls of Available-for-sale Securities Purchases of available-for-sale marketable securities Payments to Acquire Available-for-sale Securities Purchases of property, net Payments to Acquire Property, Plant, and Equipment Proceeds from sale of Board of Trade of the City of Chicago, Inc. building Proceeds from Sale of Property, Plant, and Equipment Proceeds from Divestiture of Business, net Proceeds from Divestiture of Business, net Proceeds from Divestiture of Business, net Investment in S&P/Dow Jones Indices LLC Payments to Acquire Investments Investment in DME Holdings Limited Payments to Acquire Equity Method Investments Proceeds from sale of Index Services assets Proceeds from Sale of Other Assets Other Payments for (Proceeds from) Other Investing Activities Net Cash Used in Investing Activities Net Cash Provided by (Used in) Investing Activities Cash Flows from Financing Activities Net Cash Provided by (Used in) Financing Activities [Abstract] Repayment of other borrowings Repayments of Other Debt Cash dividends Payments of Dividends Payments for Repurchase of Common Stock Payments for Repurchase of Common Stock Proceeds from exercise of stock options Proceeds from Stock Options Exercised Excess tax benefits related to employee option exercises and restricted stock vesting Excess Tax Benefit from Share-based Compensation, Financing Activities Other Proceeds from (Payments for) Other Financing Activities Net Cash Used in Financing Activities Net Cash Provided by (Used in) Financing Activities Net change in cash and cash equivalents Cash and Cash Equivalents, Period Increase (Decrease) Cash and cash equivalents, beginning of period Cash and Cash Equivalents, at Carrying Value Cash and Cash Equivalents, End of Period Supplemental Disclosure of Cash Flow Information Supplemental Cash Flow Information [Abstract] Income taxes paid Income Taxes Paid Interest paid Interest Paid Investment in S&P/Dow Jones Indices LLC Noncash or Part Noncash Acquisition, Interest Acquired Noncash or Part Noncash Acquisition, Investments Acquired Noncash or Part Noncash Acquisition, Investments Acquired Non-cash investing activities: Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Change in net unrealized securities gains Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, before Tax Remainder of 2012 Future Amortization Expense, Remainder of Fiscal Year 2013 Future Amortization Expense, Year One 2014 Future Amortization Expense, Year Two 2015 Future Amortization Expense, Year Three 2016 Future Amortization Expense, Year Four 2017 Future Amortization Expense, Year Five Thereafter Future Amortization Expense, after Year Five Debt Disclosure [Abstract] 2013 Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months 2014 Long-term Debt, Maturities, Repayments of Principal in Year Two 2015 Long-term Debt, Maturities, Repayments of Principal in Year Three 2016 Long-term Debt, Maturities, Repayments of Principal in Year Four 2017 Long-term Debt, Maturities, Repayments of Principal in Year Five Thereafter Long-term Debt, Maturities, Repayments of Principal after Year Five Intangible Assets And Goodwill Goodwill and Intangible Assets Disclosure [Text Block] Schedule Of Goodwill [Table] Schedule of Goodwill [Table] Statement, Business Segments [Axis] Statement, Business Segments [Axis] Segment [Domain] Segment [Domain] CBOT Holdings, Inc. [Member] CBOT Holdings [Member] CBOT Holdings [Member] NYMEX Holdings, Inc. [Member] NYMEX Holdings [Member] NYMEX Holdings [Member] Other [Member] Other [Member] Goodwill [Line Items] Goodwill [Line Items] Goodwill, Written off Related to Sale of Business Unit Goodwill, Written off Related to Sale of Business Unit Total Goodwill, beginning balance Goodwill Other Activity Goodwill, Translation and Purchase Accounting Adjustments Total Goodwill, ending balance Fair Value Measurements [Abstract] Fair Value Measurements [Abstract] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value by Liability Class [Axis] Fair Value by Liability Class [Axis] Contingent Consideration Type [Domain] Contingent Consideration Type [Domain] Fair Value by Asset Class [Axis] Fair Value by Asset Class [Axis] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, by Asset Class [Domain] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, by Asset Class [Domain] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Valulation Model Probability Low Range Valulation Model Probability Low Range Valulation Model Probability Low Range Valuation Model Probability High Range Valuation Model Probability High Range Valuation Model Probability High Range Debt Debt Disclosure [Text Block] Sale of Building [Abstract] Sale of Building [Abstract] Document and Entity Information [Abstract] Document and Entity Information [Abstract] Class B Common Stock, Class B-1 [Member] Class B Common Stock, Class B1 [member] Class B Common Stock, Class B1 [Member] Class B Common Stock, Class B-2 [Member] Class B Common Stock, Class B2 [member] Class B Common Stock, Class B2 [Member] Class B Common Stock, Class B-3 [Member] Class B Common Stock, Class B3 [Member] Class B Common Stock, Class B3 [Member] Class B Common Stock, Class B-4 [Member] Class B Common Stock, Class B4 [member] Class B Common Stock, Class B4 [Member] Document Type Document Type Amendment Flag Amendment Flag Document Period End Date Document Period End Date Document Fiscal Period Focus Document Fiscal Period Focus Document Fiscal Year Focus Document Fiscal Year Focus Trading Symbol Trading Symbol Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Debt Conversion [Table] Debt Conversion [Table] Short-term Debt, Type [Axis] Short-term Debt, Type [Axis] Short-term Debt, Type [Domain] Short-term Debt, Type [Domain] Commercial Paper [Member] Commercial Paper [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Weighted average balance, at par value, of commercial paper outstanding Short-term Debt, Average Outstanding Amount Maximum month-end balance for commercial paper Short-term Debt, Maximum Month-end Outstanding Amount Property [Abstract] Property [Abstract] Schedule of Significant Acquisitions and Disposals [Table] Schedule of Significant Acquisitions and Disposals [Table] Significant Acquisitions and Disposals by Transaction [Axis] Significant Acquisitions and Disposals by Transaction [Axis] Significant Acquisitions and Disposals, Transaction [Domain] Significant Acquisitions and Disposals, Transaction [Domain] Significant Acquisitions and Disposals [Line Items] Significant Acquisitions and Disposals [Line Items] Income Statement [Abstract] Revenues Revenues [Abstract] Clearing and transaction fees Clearing Fees Revenue Market data and information services Market data and information services Market Data And Information Services Access and communication fees Access and communication fees Revenue from providing access fees to customers for the use of electronic trading platform and revenue from telecommunication networks and communication services. Other Other Revenue, Net Total Revenues Revenues Expenses Costs and Expenses [Abstract] Compensation and benefits Labor and Related Expense Communications Communication Technology support services Information Technology and Data Processing Professional fees and outside services Professional Fees Occupancy and building operations Occupancy, Net Licensing and other fee agreements License Costs Other Other Cost and Expense, Operating Total Expenses Costs and Expenses Operating Income Operating Income (Loss) Non-Operating Income (Expense) Nonoperating Income (Expense) [Abstract] Investment income Investment Income, Nonoperating Gains (losses) on derivative investments Gain (Loss) on Derivative Instruments, Net, Pretax Interest and other borrowing costs Interest and Debt Expense Equity in net losses of unconsolidated subsidiaries Other nonoperating income (expense) Other Nonoperating Income (Expense) Total Non-Operating Nonoperating Income (Expense) Income before Income Taxes Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest Income tax provision Income Tax Expense (Benefit) Net Income Net Income (Loss) Attributable to Noncontrolling Interest Net Income (Loss) Attributable to Noncontrolling Interest Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest Net Income Attributable to CME Group Net Income (Loss) Attributable to Parent Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Earnings per Common Share Attributable to CME Group: Earnings Per Share [Abstract] Basic (in dollars per share) Earnings Per Share, Basic Diluted (in dollars per share) Earnings Per Share, Diluted Weighted Average Number of Common Shares: Weighted Average Number of Shares Outstanding, Diluted [Abstract] Basic (in shares) Weighted Average Number of Shares Outstanding, Basic Diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract] Schedule of Defined Benefit Plans Disclosures [Table] Schedule of Defined Benefit Plans Disclosures [Table] Fair Value by Measurement Frequency [Axis] Fair Value by Measurement Frequency [Axis] Fair Value, Measurement Frequency [Domain] Fair Value, Measurement Frequency [Domain] Fair Value, Measurements, Recurring [Member] Fair Value, Measurements, Recurring [Member] Fair Value, Hierarchy [Axis] Fair Value, Hierarchy [Axis] Fair Value Measurement [Domain] Fair Value Plan Asset Measurement [Domain] Fair Value, Inputs, Level 1 [Member] Fair Value, Inputs, Level 1 [Member] Fair Value, Inputs, Level 2 [Member] Fair Value, Inputs, Level 2 [Member] Fair Value, Inputs, Level 3 [Member] Fair Value, Inputs, Level 3 [Member] Schedule of Trading Securities and Other Trading Assets, Major Types of Trading Securities and Assets [Axis] Schedule of Trading Securities and Other Trading Assets, Major Types of Trading Securities and Assets [Axis] Major Types of Trading Securities and Assets [Domain] Major Types of Trading Securities and Assets [Domain] Mutual funds [Member] Mutual funds [Member] Mutual Funds [Member] Schedule of Available-for-sale Securities, Major Types of Debt and Equity Securities [Axis] Schedule of Available-for-sale Securities, Major Types of Debt and Equity Securities [Axis] Major Types of Debt and Equity Securities [Domain] Major Types of Debt and Equity Securities [Domain] US Treasury Securities [Member] US Treasury Securities [Member] Municipal Bonds [Member] Municipal Bonds [Member] Corporate Bonds [Member] Domestic Corporate Debt Securities [Member] Asset-backed Securities [Member] Asset-backed Securities [Member] US Government Agencies Debt Securities [Member] US Government Agencies Debt Securities [Member] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Available-for-sale Securities at Fair Value Available-for-sale Securities, Fair Value Disclosure Trading Securities at Fair Value Trading Securities, Fair Value Disclosure Marketable Securities at Fair Value Marketable Securities, Fair Value Disclosure Marketable Securities, Fair Value Disclosure Total Assets at Fair Value Assets, Fair Value Disclosure Contingent consideration at Fair Value Business Acquisition, Contingent Consideration, at Fair Value Total liabilities at fair value Liabilities, Fair Value Disclosure Schedule of Finite-Lived Intangible Assets by Major Class [Table] Schedule of Finite-Lived Intangible Assets by Major Class [Table] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets [Line Items] Finite-Lived Intangible Assets [Line Items] Number of buildings sold under plan for sale and partial leaseback (in buildings) Number of Buildings Sold Under Plan For Sale and Partial Leaseback Number of Buildings Sold Under Plan For Sale and Partial Leaseback Net book value of intangible assets sold under plan for sale and partial leaseback Intangible Assets, Net, Sold Under Plan For Sale and Partial Leaseback Intangible Assets, Net, Sold Under Plan For Sale and Partial Leaseback Contributed intangible assets Contributed intangible assets Contributed intangible assets Net book value of intangible assets sold Net book value of intangible assets sold Net book value of intangible assets sold Amortization of purchased intangibles Financial instruments measured at fair value on a recurring basis Fair Value, Measurement Inputs, Disclosure [Table Text Block] Reconciliation of assets and liabilities valued at fair value on a recurring basis using significant unobservable inputs (level 3) Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Share-based Compensation [Abstract] Stock-Based Payments Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Guarantees [Abstract] Guarantees Guarantees [Text Block] Gain (Loss) on Sale of Other Assets Sale Leaseback Transaction, Lease Terms Sale Leaseback Transaction, Lease Terms Loss Contingency [Abstract] Contingencies Contingencies Disclosure [Text Block] Clearing Firm, Market Data And Other Customer Relationships [Member] Customer Relationships [Member] Lease-Related Intangibles [Member] Lease Agreements [Member] Technology-Related Intellectual Property [Member] Developed Technology Rights [Member] Other Intangible Assets [Member] Other Intangible Assets [Member] Total Amortizable Intangible Assets [Member] Total Amortizable Intangible Assets [Member] Total amortizable intangible assets [Member] Foreign Currency Translation Adjustments [Member] Foreign Currency Translation Adjustments [Member] Foreign Currency Translation Adjustments [Member] Total Amortizable Intangible Assets, Net [Member] Total Amortizable Intangible Assets, Net [Member] Total Amortizable Intangible Assets Net [Member] Indefinite-lived Intangible Assets by Major Class [Axis] Indefinite-lived Intangible Assets by Major Class [Axis] Indefinite-lived Intangible Assets, Major Class Name [Domain] Indefinite-lived Intangible Assets, Major Class Name [Domain] Trade Names [Member] Trade Names [Member] Foreign Currency Translation Adjustments [Member] Foreign Currency Translation Adjustments Indefinite [Member] Foreign currency translation adjustments indefinite [Member] Assigned value Finite-Lived Intangible Assets, Gross Accumulated amortization Finite-Lived Intangible Assets, Accumulated Amortization Net book value Finite-Lived Intangible Assets, Net Indefinite-lived Intangible Assets Indefinite-lived Intangible Assets Other Indefinite-lived Intangible Assets Other Indefinite-lived Intangible Assets Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] $750.0 million fixed rate notes due August 2013, interest equal to 5.40% [Member] Seven Hundred Fifty Million Fixed Rate Notes Due August Two Thousand Thirteen, Interest Equal To Five Point Four Zero Percent [Member] Fixed Rate Notes Due August 2013, Interest Equal To 5.40%, $750.0 Million $750.0 million fixed rate notes due February 2014, interest equal to 5.75% [Member] Seven Hundred Fifty Million Dollar Fixed Rate Notes Due February Twenty Fourteen, Interest Equal To Five Point Seven Five Percent [Member] $750.0 Million Fixed Rate Notes Due August 2014, Interest Equal To 5.75% $612.5 million fixed rate notes due March 2018, interest equal to 4.40% [Member] Six Hundred Twelve Point Five Million Fixed Rate Notes Due March Two Thousand Eighteen, Interest Equal To Four Point Four Zero Percent [Member] $612.5 Million Fixed Rate Notes Due March 2018, Interest Equal To 4.40% Debt instrument, fair value Debt Instrument, Fair Value Disclosure Debt instrument, face amount Debt Instrument, Face Amount Debt instrument, maturity date Debt Instrument, Maturity Date Schedule Of Short-Term And Long-Term Debt Schedule of Debt [Table Text Block] Long-term debt maturities at par value Schedule of Maturities of Long-term Debt [Table Text Block] Fair value of fixed rate notes by maturity date Fair Value Of Fixed Rate Notes By Maturity Date [Text Block] Fair Value Of Fixed Rate Notes By Maturity Date [Text Block] Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Period Increase (Decrease) Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Period Increase (Decrease) Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Fair value of liability at December 31, 2011 Included in operating expense Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings Fair value of liability at June 30, 2012 Basic And Diluted Earnings Per Share Basic And Diluted Earnings Per Share [Text Block] Basic And Diluted Earnings Per Share [Text Block] Assets Assets [Abstract] Cash and cash equivalents Marketable securities Marketable Securities, Current Accounts receivable, net of allowance of $0.8 and $1.3 Accounts Receivable, Net, Current Other current assets (includes $40.0 in restricted cash) Other Assets, Current Cash performance bonds and guaranty fund contributions Good Faith and Margin Deposits with Broker-Dealers Total current assets Assets, Current Property, net of accumulated depreciation and amortization of $581.2 and $576.3 Property, Plant and Equipment, Net Intangible assets - trading products Intangible assets - other, net Intangible Assets, Net (Excluding Goodwill) Goodwill Other assets (includes $20.5 in restricted cash) Other Assets, Noncurrent Total Assets Assets Liabilities and Shareholders' Equity Liabilities and Equity [Abstract] Accounts payable Accounts Payable, Current Other current liabilities Other Liabilities, Current Cash performance bonds and guaranty fund contributions Margin Deposits And Guaranty Funds Liabilities Current Margin Deposits And Guaranty Funds Liabilities Current. Total current liabilities Liabilities, Current Long-term debt Unsecured Long-term Debt, Noncurrent Deferred income tax liabilities, net Deferred Tax Assets (Liabilities), Net, Noncurrent Other liabilities Other Liabilities, Noncurrent Total Liabilities Liabilities Redeemable non-controlling interest Temporary Equity, Carrying Amount Shareholders' Equity: Stockholders' Equity Attributable to Parent [Abstract] Preferred stock, $0.01 par value, 10,000 and 9,860 shares authorized, none issued or outstanding Preferred Stock, Value, Issued Series A junior participating preferred stock, $0.01 par value, 0 and 140 shares authorized, none issued or outstanding Series A junior participating preferred stock, $0.01 par value, 140 shares authorized, none issued or outstanding Series A junior participating preferred stock, $0.01 par value, 140 shares authorized, none issued or outstanding Common stock Common Stock, Value, Outstanding Additional paid-in capital Additional Paid in Capital, Common Stock Retained earnings Retained Earnings (Accumulated Deficit) Accumulated other comprehensive income (loss) Accumulated Other Comprehensive Income (Loss), Net of Tax Total Shareholders' Equity Stockholders' Equity Attributable to Parent Total Liabilities and Shareholders' Equity Liabilities and Equity Earnings Per Share Earnings Per Share [Text Block] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Antidilutive Securities Excluded from Computation of Earnings Per Share, by Antidilutive Securities [Axis] Antidilutive Securities Excluded from Computation of Earnings Per Share, by Antidilutive Securities [Axis] Antidilutive Securities, Name [Domain] Antidilutive Securities, Name [Domain] Stock Options [Member] Stock Options [Member] Restricted Stock [Member] Restricted Stock [Member] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount (in shares) Net Income Attributable to CME Group Effect of stock options and restricted stock awards (in shares) Effect of Stock Options Effect of Stock Options Diluted (in shares) Earnings per common share, basic (in dollars per share) Earnings per common share, diluted (in dollars per share) Fair Value Measurements Fair Value Disclosures [Text Block] Long-term debt Unsecured Debt Forward starting interest rate swap agreement 2010 fixed 4.46% Forward starting interest rate swap agreement fixed rate Forward starting interest rate swap agreement, fixed rate Stated interest rate percentage Debt Instrument, Interest Rate, Stated Percentage Subsequent Events [Abstract] Subsequent Events Subsequent Events [Text Block] Mergers, Acquisitions and Dispositions Disclosures [Text Block] Mergers, Acquisitions and Dispositions Disclosures [Text Block] Loss Contingencies by Nature of Contingency [Axis] Loss Contingencies by Nature of Contingency [Axis] Loss Contingency, Nature [Domain] Loss Contingency, Nature [Domain] Fifth Market 2008 claim Pending or Threatened Litigation [Member] Realtime Data 2009 claim Pending or Threatened Litigation Two [Member] Pending or Threatened Litigation Two [Member] MF Global Bankruptcy Litigation [Member] Pending or Threatened Litigation Three [Member] Pending or Threatened Litigation Three [Member] Number of alledged patent infringements (in patents) Number of Alledged Patent Infringements Number of Alledged Patent Infringements Number of additional related lawsuits (in lawsuits) Number of Additional Related Lawsuits Number of Additional Related Lawsuits Dropped Patents Dropped Patents Dropped Patents Asserted Patents Asserted Patents Asserted Patents Percentage of return of funds to account holders Loss Contingency, Description of Account Holders, Percentage of Return of Funds Loss Contingency, Description of Account Holders, Percentage of Return of Funds Accrued liability related to all outstanding legal matters Estimated Litigation Liability Consolidated Statements of Comprehensive Income [Abstract] Consolidated Statements of Comprehensive Income [Abstract] Other comprehensive income, net of tax Other Comprehensive Income (Loss), Net of Tax [Abstract] Net unrealized holding gains arising during the period Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, before Tax Investment securities, income tax benefit (expense) Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Tax Investment securities, net Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax Net change in defined benefit plans arising during the period Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, before Tax Amortization of net actuarial (gains) losses included in pension expense Other Comprehensive Income (Loss), Reclassification, Pension and Other Postretirement Benefit Plans, Net Gain (Loss) Recognized in Net Periodic Benefit Cost, before Tax Defined benefit plans, income tax benefit (expense) Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Tax Defined benefit plans, net Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax Net unrealized holding losses arising during the period Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax Amortization of effective portion of loss on cash flow hedge Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, before Tax Derivative instruments, income tax benefit (expense) Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax Effect Derivative instruments, net Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax Foreign currency translation adjustment Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, before Tax Foreign currency translation, income tax benefit (expense) Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax Foreign currency translation, net Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Other comprehensive income, net of tax Other Comprehensive Income (Loss), Net of Tax Comprehensive income Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Less: comprehensive income attributable to redeemable non-controlling interest Comprehensive income attributable to CME Group Comprehensive Income (Loss), Net of Tax, Attributable to Parent Schedule of Guarantor Obligations [Table] Schedule of Guarantor Obligations [Table] Guarantor Obligations by Nature [Axis] Guarantor Obligations by Nature [Axis] Guarantor Obligations, Nature [Domain] Guarantor Obligations, Nature [Domain] Family Farmer and Ranchers Protection Fund [Member] Family Farmer and Ranchers Protection Fund [Member] Family Farmer and Ranchers Protection Fund [Member] Payment and Performance Risk (Credit Rating) [Axis] Payment and Performance Risk (Credit Rating) [Axis] Credit Rating [Domain] Credit Rating [Domain] Guarantor Obligations by Underlying Asset Class [Axis] Guarantor Obligations by Underlying Asset Class [Axis] Underlying Asset Class [Domain] Underlying Asset Class [Domain] Guarantor Obligations [Line Items] Guarantor Obligations [Line Items] Payment per participant Payment per participant Payment per participant Payment per cooperative Payment per cooperative Payment per cooperative Future losses Future losses Future losses Guarantor Obligations, Maximum Exposure, Undiscounted Guarantor Obligations, Maximum Exposure, Undiscounted Average daily clearing settlement Average Daily Clearing Settlement Average Daily Clearing Settlement Agreement automatic renewal period (in years) Agreement Automatic Renewal, Period Agreement Automatic Renewal, Period Contingent liability to SGX, amount of irrevocable letters of credit Guarantor Obligations, Collateral Held Directly or by Third Parties Percentage allocated to CME and OCC of gains (losses) on liquidation of open position and cross margin account Percentage Allocated To Parent And External Party Of Cross Margin Arrangement Of Gains Losses On Liquidation Of Open Position And Cross Margin Account Percentage allocated to parent and external party of cross-margin arrangement of gains (losses) on liquidation of open position and cross-margin account Guarantor obligations, current carrying value Guarantor Obligations, Current Carrying Value Maximum payment to trustee under event of over distribution of property than permitted by bankruptcy code and CFTC regulations Maximum Payment to Trustee Under Event of Over Distribution of Property Than Permitted by Bankruptcy Code and CFTC Regulations Maximum Payment to Trustee Under Event of Over Distribution of Property Than Permitted by Bankruptcy Code and CFTC Regulations Subsequent Event [Table] Subsequent Event [Table] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Sale Leaseback of Chicago Buildings[Member] New Contract [Member] Subsequent Event [Line Items] Subsequent Event [Line Items] Sale leaseback transaction, lease period (in years) Sale Leaseback Transaction, Lease Period Sale Leaseback Transaction, Lease Period Fund to Provide Further Protection of Customer Segregated Funds for US Family Farmers and Ranchers Fund to Provide Further Protection of Customer Segregated Funds for US Family Farmers and Ranchers Fund to Provide Further Protection of Customer Segregated Funds for US Family Farmers and Ranchers who hedge their business in CME Group futures markets. Statement of Stockholders' Equity [Abstract] Statement, Equity Components [Axis] Statement, Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Common Stock And Additional Paid-In Capital [Member] Common Stock Including Additional Paid in Capital [Member] Retained Earnings [Member] Retained Earnings [Member] Accumulated Other Comprehensive Income (Loss) [Member] Accumulated Other Comprehensive Income (Loss) [Member] Balance (in shares) Balance Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Dividends on common stock per share Dividends, Cash Stock Repurchased During Period, Shares Stock Repurchased During Period, Shares Stock Repurchased During Period, Value Stock Repurchased During Period, Value Exercise of stock options (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Exercise of stock options Stock Issued During Period, Value, Stock Options Exercised Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation Vesting of issued restricted Class A common stock (in shares) Vesting Of Issued Restricted Stock Number of shares issued during the period as a result of the vesting of restricted stock units. Vesting of issued restricted Class A common stock Vesting Of Issued Restricted Stock Value Vesting Of Issued Restricted Stock Stock Issued To Related Parties During Period Shares Stock Issued To Related Parties During Period Shares Number of shares of stock issued during the period to related parties. Stock Issued To Related Parties During Period Value Stock Issued To Related Parties During Period Value Value of stock issued during the period to related parties. Stock Issued During Period, Shares, Employee Stock Purchase Plans Stock Issued During Period, Shares, Employee Stock Purchase Plans Stock Issued During Period, Value, Employee Stock Purchase Plan Stock Issued During Period, Value, Employee Stock Purchase Plan Stock-based compensation Stock Granted During Period, Value, Share-based Compensation, Net of Forfeitures Balance (in shares) Balance Property, Plant and Equipment Disclosure [Text Block] Property, Plant and Equipment Disclosure [Text Block] Basis of Presentation [Abstract] Basis of Presentation [Abstract] Report Date [Axis] Report Date [Axis] Financial Statements Date [Domain] Financial Statements Date [Domain] Adjustments for New Accounting Pronouncements [Axis] Adjustments for New Accounting Pronouncements [Axis] Type of Adoption [Domain] Type of Adoption [Domain] Adjustments for Change in Accounting Principle [Axis] Adjustments for Change in Accounting Principle [Axis] Adjustments for Change in Accounting Principle [Domain] Adjustments for Change in Accounting Principle [Domain] Adjustments for Error Corrections [Axis] Adjustments for Error Corrections [Axis] Adjustments for Error Correction [Domain] Adjustments for Error Correction [Domain] Cash dividends on common stock, per share (in dollars per share) Common Stock, Dividends, Per Share, Cash Paid Organization, Consolidation and Presentation of Financial Statements [Abstract] Basis Of Presentation Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum [Member] Minimum [Member] Maximum [Member] Maximum [Member] Total expense for stock-based payments Allocated Share-based Compensation Expense Income tax benefit for stock-based payment arrangements Employee Service Share-based Compensation, Tax Benefit from Compensation Expense Stock options, granted, shares Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures Stock options, term in years Share-based Compensation Arrangement by Share-based Payment Award, Expiration Date Exercise price, per share Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price Fair value, options Fair Value, Options Fair Value Options Fair value assumptions, method used Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Method Used Vesting period, years Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Stock option valuation assumption, dividend yield Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate Stock option valuation assumption, expected volatility Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate Stock option valuation assumption, risk-free interest rate Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate Stock option valuation assumption, expected life, in years Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term Grant date weighted average fair value of options granted Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Grants of restricted Class A common stock, shares Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Grants of restricted stock units, shares Share Based Compensation Arrangement By Share Based Payment Award Restricted Stock Units Grants In Period Share Based Compensation Arrangement By Share Based Payment Award Restricted Stock Units Grants In Period Share based compensation arrangement by share based payment award, award vesting period lower range, years Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period, Minimum Share based compensation arrangement by share based payment award, award vesting period upper range, years Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period, Maximum Restricted Class A common stock, fair value of grants Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Total Fair Value Company granted performance shares Share Based Compensation Arrangement By Company Granted Performance Shares Share Based Compensation Arrangement By Company Granted Performance Shares Expense for performance shares recognized on accelerated basis over vesting period Expense For Performance Shares Recognized On Accelerated Basis Over Vesting Period Expense for performance shares recognized on accelerated basis over vesting period.