Debt Disclosure [Abstract] Debt Debt Disclosure [Text Block] Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract] 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] 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] Proceeds from sale of Board of Trade of the City of Chicago, Inc. building Proceeds from Sale of Property, Plant, and Equipment Sale of Building [Abstract] Sale of Building [Abstract] Gain (Loss) on Sale of Other Assets Gain (Loss) on Sale of Other Assets Sale Leaseback Transaction, Lease Terms Sale Leaseback Transaction, Lease Terms 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] Valuation model discount rate Valuation model discount rate Valuation model discount rate 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 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] S&P/Dow Jones Indices LLC [Member] S&P/Dow Jones Indices LLC [Member] S&P/Dow Jones Indices LLC [Member] 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 Equity Method Investments Equity Method Investments Proceeds from Divestiture of Businesses Proceeds from Divestiture of Businesses Investment Owned, at Fair Value Investment Owned, at Fair Value 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 Subsequent Events [Abstract] Subsequent Event [Table] Subsequent Event [Table] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] Class A Common Stock [Member] Common Class A [Member] 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] Goodwill and Intangible Assets Disclosure [Abstract] 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. 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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 Mergers, Acquisitions and Dispositions Disclosures [Text Block] Mergers, Acquisitions and Dispositions Disclosures [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] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum [Member] Minimum [Member] Maximum [Member] Maximum [Member] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] 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. Income Tax Disclosure [Abstract] 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 Loss Contingency [Abstract] Contingencies Contingencies Disclosure [Text Block] Income Taxes Income Tax Disclosure [Text Block] 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) Common Stock, Shares, Outstanding Balance Net Income Attributable to CME Group Net Income (Loss) Attributable to Parent Other comprehensive income attributable to CME Group 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 Excess tax benefits from option exercises and restricted stock vesting 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 Shares issued to Board of Directors (in shares) Stock Issued To Related Parties During Period Shares Number of shares of stock issued during the period to related parties. Shares issued to Board of Directors Stock Issued To Related Parties During Period Value Value of stock issued during the period to related parties. Shares issued under Employee Stock Purchase Plan (in shares) Stock Issued During Period, Shares, Employee Stock Purchase Plans Shares issued under 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 Consolidated Statements of Comprehensive Income [Abstract] Consolidated Statements of Comprehensive Income [Abstract] Statement, Scenario [Axis] Statement, Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest 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 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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 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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 Guarantee Collateral Guarantee Collateral 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 Derivative Instruments and Hedging Activities Disclosure [Text Block] Derivative Instruments and Hedging Activities Disclosure [Text Block] 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 Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest Net Income Attributable to CME Group 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: 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 Basis of Presentation [Abstract] Basis of Presentation [Abstract] Schedule of Short-term Debt [Table Text Block] Schedule of Short-term Debt [Table Text Block] Schedule Of Short-Term And Long-Term Debt Schedule of Long-term Debt Instruments [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] 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] Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount (in shares) 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) Debt Conversion [Table] Debt Conversion [Table] Commercial Paper [Member] Commercial Paper [Member] Forward starting interest rate swap agreement fixed rate Forward starting interest rate swap agreement fixed rate Forward starting interest rate swap agreement, fixed rate Debt Instrument, Interest Rate, Stated Percentage Debt Instrument, Interest Rate, Stated Percentage 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 Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Derivative Instrument Risk [Axis] Derivative Instrument Risk [Axis] Derivative Contract Type [Domain] Derivative Contract Type [Domain] Hedging Designation [Axis] Hedging Designation [Axis] Hedging Designation [Domain] Hedging Designation [Domain] Derivatives, Fair Value, by Balance Sheet Location [Axis] Derivatives, Fair Value, by Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Derivatives, Fair Value [Line Items] Derivatives, Fair Value [Line Items] Derivative Liability, Fair Value, Gross Liability Subsequent Events Subsequent Events [Text Block] Derivative Instruments, Gain (Loss) by Hedging Relationship, by Income Statement Location, by Derivative Instrument Risk [Table] Derivative Instruments, Gain (Loss) by Hedging Relationship, by Income Statement Location, by Derivative Instrument Risk [Table] Derivative Instruments, Gain (Loss) by Income Statement Location [Axis] Derivative Instruments, Gain (Loss) by Income Statement Location [Axis] Income Statement and Other Comprehensive Income (Loss) Location [Domain] Income Statement and Other Comprehensive Income (Loss) Location [Domain] Derivative Instruments, Gain (Loss) by Hedging Relationship [Axis] Derivative Instruments, Gain (Loss) by Hedging Relationship [Axis] Hedging Relationship [Domain] Hedging Relationship [Domain] Derivative Instruments, Gain (Loss) [Line Items] Derivative Instruments, Gain (Loss) [Line Items] Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, before Tax Gain (Loss) on Derivative Instruments, Net, Pretax 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] 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 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 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 Contingent obligation arising from acquisition Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Period Increase (Decrease) Included in operating expense Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings Fair value of liability at September 30, 2012 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 Long-term debt Unsecured Debt Fair Value Measurements Fair Value Disclosures [Text Block] Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block] Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block] Schedule of Derivative Instruments, Effect on Other Comprehensive Income (Loss) [Table Text Block] Schedule of Derivative Instruments, Effect on Other Comprehensive Income (Loss) [Table Text Block]