Statement of Cash Flows [Abstract] Statement [Table] Statement [Table] Restatement [Axis] Restatement [Axis] Restatement [Domain] Restatement [Domain] Statement [Line Items] Statement [Line Items] 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 Unrealized loss on assets held for sale Other Asset Impairment Charges Net loss on derivatives Unrealized Gain (Loss) on Derivatives Net realized and unrealized (gains) losses on investments Gain (Loss) on Investments Undistributed net earnings of unconsolidated subsidiaries Income (Loss) from Equity Method Investments, Net of Dividends or Distributions 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 (Used in) 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 Debt Securities, Available-for-sale 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 sales of investments Proceeds from Sale and Maturity of Other Investments 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] Issuance of commercial paper, net of maturities Proceeds from (Repayments of) Commercial Paper Proceeds from debt, net of issuance costs Proceeds from Issuance of Long-term Debt Repayments of debt Repayments of Long-term Debt Cash dividends Payments of Dividends Premium payment for derivative contract Payments for Derivative Instrument, Financing Activities Settlement of derivative contracts Payments for (Proceeds from) Derivative Instrument, Financing Activities Employee taxes paid on restricted stock vesting Payments Related to Tax Withholding for Share-based Compensation 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, cash equivalents and restricted cash Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, beginning balance Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, ending balance Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Short-term restricted cash Restricted Cash and Cash Equivalents, Current Long-term restricted cash Restricted Cash and Cash Equivalents, Noncurrent Income taxes paid Income Taxes Paid Interest paid Interest Paid, Including Capitalized Interest, Operating and Investing Activities Debt Disclosure [Abstract] 2020 Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months 2021 Long-term Debt, Maturities, Repayments of Principal in Year Two 2022 Long-term Debt, Maturities, Repayments of Principal in Year Three 2023 Long-term Debt, Maturities, Repayments of Principal in Year Four 2024 Long-term Debt, Maturities, Repayments of Principal in Year Five Thereafter Long-term Debt, Maturities, Repayments of Principal after Year Five Leases [Abstract] Lease Arrangement, Type [Axis] Lease Arrangement, Type [Axis] Lease Arrangement, Type [Domain] Lease Arrangement, Type [Domain] Finance Lease, Right-of-Use Asset Finance Lease, Right-of-Use Asset Operating Lease, Right-of-Use Asset Operating Lease, Right-of-Use Asset Operating Lease, Liability, Current Operating Lease, Liability, Current Operating Lease, Liability, Noncurrent Operating Lease, Liability, Noncurrent Operating Lease, Liability Operating Lease, Liability Operating Lease, Weighted Average Remaining Lease Term Operating Lease, Weighted Average Remaining Lease Term Operating Lease, Weighted Average Discount Rate, Percent Weighted Average Discount Rate Operating Lease Weighted Average Discount Rate Operating Lease Finance Lease, Liability, Current Finance Lease, Liability, Current Finance Lease, Liability, Noncurrent Finance Lease, Liability, Noncurrent Finance Lease, Liability Finance Lease, Liability Finance Lease, Weighted Average Remaining Lease Term Finance Lease, Weighted Average Remaining Lease Term Finance Lease, Weighted Average Discount Rate, Percent Finance Lease, Weighted Average Discount Rate, Percent Fair Value by Fair Value Hierarchy Level Extensible List [Abstract] Fair Value Measurements Fair Value Disclosures [Text Block] Schedule of Short-term Debt [Table] Schedule of Short-term Debt [Table] Short-term Debt, Type [Axis] Short-term Debt, Type [Axis] Short-term Debt, Type [Domain] Short-term Debt, Type [Domain] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Short-term Debt [Line Items] Short-term Debt [Line Items] 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] 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] Schedule of Goodwill [Table] Schedule of Goodwill [Table] Consolidation Items [Axis] Consolidation Items [Axis] Consolidation Items [Domain] Consolidation Items [Domain] Segments [Axis] Segments [Axis] Segments [Domain] Segments [Domain] Income Statement Location [Axis] Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Reporting Unit [Axis] Reporting Unit [Axis] Reporting Unit [Domain] Reporting Unit [Domain] Goodwill [Line Items] Goodwill [Line Items] Goodwill Disclosure [Text Block] Goodwill Disclosure [Text Block] Guarantees [Abstract] Schedule of Guarantor Obligations [Table] Schedule of Guarantor Obligations [Table] Guarantor Obligations, Nature [Axis] Guarantor Obligations, 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] Guarantor Obligations [Line Items] Guarantor Obligations [Line Items] 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 Payment per participant PaymentPerParticipant PaymentPerParticipant Payment per cooperative PaymentPerCooperative PaymentPerCooperative FutureLosses FutureLosses FutureLosses Payments under Guarantee Payments under Guarantee Payments under Guarantee Guarantor Obligations, Maximum Exposure, Undiscounted Guarantor Obligations, Maximum Exposure, Undiscounted CBOT [Member] CBOT [Member] CBOT [Member] NYMEX [Member] NYMEX [Member] NYMEX [Member] NEX [Member] NEX [Member] NEX [Member] Consolidated Entities [Member] Consolidated Entities [Member] Goodwill [Member] Goodwill [Member] Goodwill Goodwill Goodwill, Acquired During Period Goodwill, Acquired During Period Goodwill, Other Increase (Decrease) Goodwill, Other Increase (Decrease) Operating Lease, Cost Operating Lease, Cost Short-term Lease, Cost Short-term Lease, Cost Operating Lease, Expense Operating Lease, Expense Finance Lease, Interest Expense Finance Lease, Interest Expense Finance Lease, Right-of-Use Asset, Amortization Finance Lease, Right-of-Use Asset, Amortization Finance Lease, Expense Finance Lease, Expense Finance Lease, Expense Sublease Income Sublease Income Subsequent Events [Abstract] Subsequent Event [Table] Subsequent Event [Table] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event [Line Items] Subsequent Event [Line Items] Subsequent Events [Text Block] Subsequent Events [Text Block] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Other Comprehensive Income Location [Axis] Other Comprehensive Income Location [Axis] Other Comprehensive Income Location [Domain] Other Comprehensive Income Location [Domain] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Financial instruments measured at fair value on a recurring basis Fair Value Measurement and Measurement Inputs, Recurring and Nonrecurring [Text Block] Fair Value, Liabilities Measured on Recurring and Nonrecurring Basis [Table Text Block] Fair Value, Liabilities Measured on Recurring and Nonrecurring Basis [Table Text Block] Fair value of Debt Instruments Fair value of Debt Instruments [Table Text Block] [Table Text Block] for Fair value of Debt Instruments [Table] Fair Value Disclosures [Abstract] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Asset Class [Axis] Asset Class [Axis] Asset Class [Domain] 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] Business Combination, Contingent Consideration, Liability Business Combination, Contingent Consideration, Liability Unrealized losses included in other non-operating (income) expense Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge Goodwill, Purchase Accounting Adjustments Goodwill, Purchase Accounting Adjustments Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements Earnings Per Share [Abstract] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Antidilutive Securities Excluded from Computation of Earnings Per Share, by Antidilutive Securities [Axis] Antidilutive Securities [Axis] Antidilutive Securities, Name [Domain] Antidilutive Securities, Name [Domain] Restricted Stock [Member] Restricted Stock [Member] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Anti-dilutive securities Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Operating Lease, Weighted Average Remaining Lease Term Operating Lease, Remaining Lease Term Operating Lease, Remaining Lease Term Lessee, Operating Lease, Renewal Term Operating Lease Renewal Term Operating Lease Renewal Term Lessee, Operating Lease, Option to Terminate Operating Lease, Option to Early Terminate, Months Operating Lease, Option to Early Terminate, Months Lessee, Operating Lease, Term of Contract Operating Lease Term of Contract Operating Lease Term of Contract Lease Term Recognition-Balance Sheet Lease Term Recognition-Balance Sheet Lease Term Recognition-Balance Sheet Lessee, Leases [Policy Text Block] Lessee, Leases [Policy Text Block] Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract] Schedule of Accumulated Other Comprehensive Income (Loss) Comprehensive Income (Loss) Note [Text Block] Revenue Recognition [Abstract] Deferred Revenue Deferred Revenue Product and Service [Axis] Product and Service [Axis] Product and Service [Domain] Product and Service [Domain] Clearing and transaction fees [Member] clearing and transaction fees [Member] clearing and transaction fees [Member] Market data and information services MarketData [Member] MarketData [Member] Other OtherRevenue [Member] OtherRevenue [Member] Derivative Instrument [Axis] Derivative Instrument [Axis] Derivative Contract [Domain] Derivative Contract [Domain] Interest rate [Member] Interest Rate [Member] Interest Rate [Member] Equities [Member] Equities [Member] Equities [Member] Foreign Exchange [Member] Foreign Exchange [Member] Agricultural commodity [Member] Agricultural commodity [Member] Agricultural commodity [Member] Energy [Member] Energy [Member] Energy [Member] Metal [Member] Metal [Member] Metal [Member] Cash Markets [Member] Cash Markets [Member] Cash Markets [Member] Interest rate swap [Member] Over the Counter [Member] Timing of Transfer of Good or Service [Axis] Timing of Transfer of Good or Service [Axis] Timing of Transfer of Good or Service [Domain] Timing of Transfer of Good or Service [Domain] Services transferred at a point in time [Member] Transferred at Point in Time [Member] Services transferred over time [Member] Transferred over Time [Member] One-time charges and miscellaneous revenues [Member] One-time charges and miscellaneous revenues [Member] One-time charges and miscellaneous revenues [Member] Revenues Revenue from Contract with Customer, Excluding Assessed Tax Total Revenues Revenues Net Income (Loss) Attributable to CME Group Net Income (Loss) Attributable to Parent Basic (in shares) Weighted Average Number of Shares Outstanding, Basic Effect of stock options, restricted stock and performance shares Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Earnings per common share, basic (in dollars per share) Earnings Per Share, Basic Earnings per common share, diluted (in dollars per share) Earnings Per Share, Diluted Statement of Financial Position [Abstract] 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] Class B Common Stock [Member] Common Class B [Member] Assets Assets [Abstract] Marketable securities Marketable Securities, Current Accounts receivable, net of allowance of $2.9 and $2.7 Accounts Receivable, Net, Current Other current assets (includes $5.1 and $1.5 in restricted cash) Other Assets, Current 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 $837.3 and $761.1 Property, Plant and Equipment, Net Intangible assets—trading products Other Indefinite-lived Intangible Assets Intangible assets—other, net Intangible Assets, Net (Excluding Goodwill) Other assets (includes $0.9 and $1.2 in restricted cash) Other Assets, Noncurrent Total Assets Assets Liabilities and Equity Liabilities and Equity [Abstract] Accounts payable Accounts Payable, Current Short-term Debt Short-term Debt Other current liabilities Other Liabilities, Current 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 Liabilities, Net, Noncurrent Other liabilities Other Liabilities, Noncurrent Total Liabilities Liabilities Shareholders' Equity: Stockholders' Equity Attributable to Parent [Abstract] Preferred stock, $0.01 par value, 10,000 shares authorized at September 30, 2019 and December 31, 2018; none issued Preferred Stock, Value, Issued 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 CME Group Shareholders’ Equity Stockholders' Equity Attributable to Parent Stockholders' Equity Attributable to Noncontrolling Interest Stockholders' Equity Attributable to Noncontrolling Interest Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Total Liabilities and Equity Liabilities and Equity €350.0 million fixed rate notes due March 2019 [Member] €350.0 million fixed rate notes due March 2019 [Member] €350.0 million fixed rate notes due March 2019 [Member] ¥19.1 billion term loan due March 2019 [Member] ¥19.1 billion term loan due March 2019 [Member] ¥19.1 billion term loan due March 2019 [Member] $750.0 million Fixed Rate Notes Due September 2022, stated rate of 3.00% [Member] $750.0 million Fixed Rate Notes Due September 2022 Interest Equal To 3.00% [Member] $750.0millionFixedRateNotesDueSeptember2022InterestEqualTo3.00% €15.0 million fixed rate notes due May 2023 [Member] €15.0 million fixed rate notes due May 2023 [Member] €15.0 million fixed rate notes due May 2023 [Member] $750.0 Million Fixed Rate Notes Due March 2025, stated rate of 3.00% [Member] $750.0 Million Fixed Rate Notes Due March 2025, Interest Equal To 3.00% [Member] Seven Hundred Fifty Million Fixed Rate Notes Due March Two Thousand Twenty Five, Interest Equal To Three Point Zero Percent [Member] [Member] [Member] $500.0 Million Fixed Rate Notes Due June 2028, stated rate of 3.75% [Member] [Domain] $500.0 Million Fixed Rate Notes Due June 2028, Interest Equal To 3.75% [Member] [Domain] $500.0 Million Fixed Rate Notes Due June 2028, Interest Equal To 3.75% [Member] [Domain] $750.0 million Fixed Rate Notes Due September 2043, stated rate of 5.30% [Member] $750.0 million Fixed Rate Notes Due September 2043 Interest Equal To 5.3% [Member] $750.0millionFixedRateNotesDueSeptember2043InterestEqualTo5.3% $700.0 Million Fixed Rate Notes Due June 2048, stated rate of 4.15% [Member] [Domain] [Domain] $700.0 Million Fixed Rate Notes Due June 2048, Interest Equal To 4.15% [Member] [Domain] [Domain] $700.0 Million Fixed Rate Notes Due June 2048, Interest Equal To 4.15% [Member] [Domain] [Domain] Commercial Paper [Member] Commercial Paper [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] 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, Face Amount Debt Instrument, Face Amount Debt Instrument, Maturity Date Debt Instrument, Maturity Date Debt Instrument, Interest Rate, Stated Percentage Debt Instrument, Interest Rate, Stated Percentage Schedule of Defined Benefit Plans Disclosures [Table] Schedule of Defined Benefit Plans Disclosures [Table] Measurement Frequency [Axis] 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 and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [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] Financial Instrument [Axis] Major Types of Trading Securities and Assets [Domain] Financial Instruments [Domain] Corporate Debt Securities [Member] Corporate Debt Securities [Member] Mutual Funds [Member] Mutual Fund [Member] Equity Securities [Member] Equity Securities [Member] Asset-backed Securities [Member] Asset-backed Securities [Member] U.S. Treasury Performance Bond [Member] U.S. Treasury Performance Bond [Member] U.S. Treasury Performance Bond [Member] U.S. Government Agency Security Performance Bond [Member] U.S. Government Agency Security Performance Bond [Member] U.S. Government Agency Security Performance Bond [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 Trading Securities at Fair Value Debt Securities, Trading, and Equity Securities, FV-NI Marketable Securities Marketable Securities Total Assets at Fair Value Assets, Fair Value Disclosure Derivative Contract Liability Fair Value Hedge Liabilities Total Liabilities at Fair Value Financial and Nonfinancial Liabilities, Fair Value Disclosure New Accounting Pronouncements and Changes in Accounting Principles [Abstract] Statement of Stockholders' Equity [Abstract] Cash dividends on common stock, per share (in dollars per share) Common Stock, Dividends, Per Share, Cash Paid Loss Contingency [Abstract] Contingencies Contingencies Disclosure [Text Block] Lessee, Lease, Description [Table] Lessee, Lease, Description [Table] Property Subject to Operating Lease [Member] Property Subject to Operating Lease [Member] Property Subject to Finance Lease [Member] Property Subject to Finance Lease [Member] Property Subject to Finance Lease [Member] Lessee, Lease, Description [Line Items] Lessee, Lease, Description [Line Items] Lease, Cost [Table Text Block] Lease, Cost [Table Text Block] Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Schedule of Amounts Recognized in Balance Sheet [Table Text Block] Schedule of Amounts Recognized in Balance Sheet [Table Text Block] Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block] Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block] Schedule of Future Minimum Lease Payments for Capital Leases [Table Text Block] Schedule of Future Minimum Lease Payments for Capital Leases [Table Text Block] Accounting Changes [Text Block] Accounting Changes [Text Block] Schedule of Accumulated Other Comprehensive Income (Loss) Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Income Statement [Abstract] Revenues Revenues [Abstract] Expenses Costs and Expenses [Abstract] Compensation and benefits Labor and Related Expense Technology Information Technology and Data Processing Professional fees and outside services Professional Fees Licensing and other fee agreements LicensingFees LicensingFees 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 Interest and other borrowing costs Interest and Debt Expense Equity in net earnings of unconsolidated subsidiaries Income (Loss) from Equity Method Investments Other non-operating income (expense) Other Nonoperating Income (Expense) Total Non-Operating Income (Expense) Nonoperating Income (Expense) Income before Income Taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Income tax provision Income Tax Expense (Benefit) Net (Income) Loss Attributable to Noncontrolling Interest Net Income (Loss) Attributable to Noncontrolling Interest Earnings per Common Share Attributable to CME Group: Basic (in dollars per share) Diluted (in dollars per share) Weighted Average Number of Common Shares: Weighted Average Number of Shares Outstanding, Diluted [Abstract] Diluted (in shares) Preferred Stock [Member] Preferred Stock [Member] Accounts receivable, allowance Allowance for Doubtful Accounts Receivable, Current Accumulated depreciation and amortization, property Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment 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 Guarantees Guarantees [Text Block] Organization, Consolidation and Presentation of Financial Statements [Abstract] Basis Of Presentation Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Earnings Per Share Earnings Per Share [Text Block] Debt Debt Disclosure [Text Block] Schedule of Finite-Lived Intangible Assets [Table] Schedule of Finite-Lived Intangible Assets [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] Clearing Firm, Market Data And Other Customer Relationships [Member] Customer Relationships [Member] Technology-Related Intellectual Property [Member] Developed Technology Rights [Member] Other [Member] Other Intangible Assets [Member] Total Amortizable Intangible Assets [Member] Finite-Lived Intangible Assets [Member] Indefinite-lived Intangible Assets by Major Class [Axis] Indefinite-lived Intangible Assets [Axis] Indefinite-lived Intangible Assets, Major Class Name [Domain] Indefinite-lived Intangible Assets, Major Class Name [Domain] Trade Names [Member] Trade Names [Member] Intangible Assets [Line Items] Finite-Lived Intangible Assets [Line Items] Assigned Value Finite-Lived Intangible Assets, Gross Accumulated amortization Finite-Lived Intangible Assets, Accumulated Amortization Net book value Finite-Lived Intangible Assets, Net Total intangible assets - other, net Indefinite-lived Intangible Assets (Excluding Goodwill) Remainder of 2019 Finite-Lived Intangible Assets, Amortization Expense, Remainder of Fiscal Year 2020 Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months 2021 Finite-Lived Intangible Assets, Amortization Expense, Year Two 2022 Finite-Lived Intangible Assets, Amortization Expense, Year Three 2023 Finite-Lived Intangible Assets, Amortization Expense, Year Four 2024 Finite-Lived Intangible Assets, Amortization Expense, Year Five Thereafter Finite-Lived Intangible Assets, Amortization Expense, after Year Five Cover page. 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 Document Quarterly Report Document Quarterly Report Document Period End Date Document Period End Date Document Transition Report Document Transition Report Entity File Number Entity File Number Entity Registrant Name Entity Registrant Name Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Entity Tax Identification Number Entity Tax Identification Number Entity Address, Street Address Entity Address, Address Line One Entity Address, City Entity Address, City or Town Entity Address, State Entity Address, State or Province Entity Address, Postal Zip Code Entity Address, Postal Zip Code City Area Code City Area Code Local Phone Number Local Phone Number Entity Current Reporting Status Entity Current Reporting Status Entity Interactive Data Current Entity Interactive Data Current Entity Filer Category Entity Filer Category Entity Small Business Entity Small Business Entity Emerging Growth Company Entity Emerging Growth Company Entity Shell Company Entity Shell Company Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Title of each class Title of 12(b) Security Trading symbol Trading Symbol Name of each exchange on which registered Security Exchange Name Document Fiscal Period Focus Document Fiscal Period Focus Document Fiscal Year Focus Document Fiscal Year Focus Current Fiscal Year End Date Current Fiscal Year End Date Entity Central Index Key Entity Central Index Key Amendment Flag Amendment Flag Nonrecurring fair value [Abstract] Nonrecurring fair value [Abstract] Investment Type [Axis] Investment Type [Axis] Investments [Domain] Investments [Domain] Investment 1 [Member] Investment 1 [Member] Investment 1 [Member] Investment 2 [Member] Investment 2 [Member] Investment 2 [Member] Minimum [Member] Minimum [Member] Maximum [Member] Maximum [Member] Other than Temporary Impairment Losses, Investments Other than Temporary Impairment Losses, Investments Investment Owned, at Fair Value Investment Owned, at Fair Value Tangible Asset Impairment Charges Tangible Asset Impairment Charges Other Assets, Fair Value Disclosure Other Assets, Fair Value Disclosure Assets Held-for-sale, Long Lived, Fair Value Disclosure Assets Held-for-sale, Long Lived, Fair Value Disclosure Statement of Comprehensive Income [Abstract] Other comprehensive income (loss), net of tax: Other Comprehensive Income (Loss), Net of Tax [Abstract] Net unrealized holding gains (losses) arising during the period Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, before Tax Reclassification of net (gains) losses on sales included in investment income Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, before Tax Income tax benefit (expense) Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, Tax Investment securities, net Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, after Tax Net change in defined benefit plans arising during the period Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax Amortization of net actuarial (gains) losses included in compensation and benefits expense Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax Income tax benefit (expense) Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax Defined benefit plans, net Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax Net unrealized holding gains (losses) during the period Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax Amortization of effective portion of net (gains) losses on cash flow hedges included in interest expense Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax Income tax benefit (expense) Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax Derivative investments, net Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax Foreign currency translation adjustments Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, before Tax 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 (loss), net of tax Other Comprehensive Income (Loss), Net of Tax Comprehensive Income Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Comprehensive (Income) Loss Attributable to Noncontrolling Interest Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest Comprehensive Income attributable to CME Group Comprehensive Income (Loss), Net of Tax, Attributable to Parent Intangible Assets And Goodwill Goodwill and Intangible Assets Disclosure [Text Block] Performance Bonds and Guaranty Fund Contributions [Abstract] Performance Bonds and Guaranty Fund Contributions [Abstract] Performance Bonds and Guaranty Fund Contributions Performance Bonds and Guaranty Fund Contributions [Text Block] Performance Bonds and Guaranty Fund Contributions [Text Block] Revenue Recognition, Deferred Revenue [Policy Text Block] Revenue Recognition, Deferred Revenue [Policy Text Block] Debt Instrument, Fair Value Disclosure Debt Instrument, Fair Value Disclosure Amortization of purchased intangibles Impairment of Intangible Assets, Finite-lived Impairment of Intangible Assets, Finite-lived Statement, Equity Components [Axis] 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] AOCI Attributable to Parent [Member] Parent [Member] Parent [Member] Noncontrolling Interest [Member] Noncontrolling Interest [Member] Balance (in shares) Balance Balance Nonredeemable Noncontrolling Interest Balance Dividends on common stock 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