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performance shares Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Other comprehensive income (loss) before reclassifications and income tax benefit (expense) Other Comprehensive Income (Loss), before Reclassifications, before Tax Basic (in shares) Weighted Average Number of Shares Outstanding, Basic Operating Lease, Right-of-Use Asset Operating Lease, Right-of-Use Asset Statement, Equity Components [Axis] Equity Components [Axis] Net realized and unrealized losses on investments Gain (Loss) on Investments Derivative Investments [Member] Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] Guarantor Obligations, Maximum Exposure, Undiscounted Guarantor Obligations, Maximum Exposure, Undiscounted Finance Lease, Expense Finance Lease, Expense Finance Lease, Expense Total CME Group Shareholders’ Equity Balance Balance Stockholders' Equity Attributable to Parent Amortization of purchased intangibles Amortization of purchased intangibles Amortization of Intangible Assets Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Other liabilities Increase (Decrease) in Other Operating Liabilities Stock-based compensation Shares Granted, Value, Share-based Payment Arrangement, before Forfeiture Fair Value Measurements Fair Value Disclosures [Text Block] Trading Securities at Fair Value Debt Securities, Trading, and Equity Securities, FV-NI Intangible Assets [Line Items] Finite-Lived Intangible Assets [Line Items] Class B Common Stock, Class B-2 [Member] Class B Common Stock, Class B2 [member] Class B Common Stock, Class B2 [Member] Lease, Cost [Table Text Block] Lease, Cost [Table Text Block] Proceeds from sales of investments Proceeds from Sale of Other Investments Investment Type [Axis] Investment Type [Axis] Assigned Value Finite-Lived Intangible Assets, Gross Debt Instrument, Redemption, Period [Axis] Debt Instrument, Redemption, Period [Axis] Preferred stock, $0.01 par value, 10,000 shares authorized at September 30, 2020 and December 31, 2019; none issued Preferred Stock, Value, Issued Variable Rate [Axis] Variable Rate [Axis] Name of each exchange on which registered Security Exchange Name Anti-dilutive securities Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Depreciation and amortization Depreciation Class B Common Stock, Class B-1 [Member] Class B Common Stock, Class B1 [member] Class B Common Stock, Class B1 [Member] Lease Arrangement, Type [Domain] Lease Arrangement, Type [Domain] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Comprehensive income Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Additional paid-in capital Additional Paid in Capital, Common Stock Net Cash Provided by (Used in) Operating Activities Net Cash Provided by (Used in) Operating Activities Lessee, Operating Lease, Renewal Term Operating Lease Renewal Term Operating Lease Renewal Term Equity Component [Domain] Equity Component [Domain] Document Transition Report Document Transition Report 2021 Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months Common stock Common Stock, Value, Outstanding Finance Lease, Principal Payments Finance Lease, Principal Payments U.S. Treasury Performance Bond [Member] U.S. Treasury Performance Bond [Member] U.S. Treasury Performance Bond [Member] Contingent liability to SGX, amount of irrevocable letters of credit Guarantee Collateral Guarantee Collateral Foreign Exchange [Member] Foreign Exchange [Member] 2023 Operating Leases, Future Minimum Payments, Due in Three Years Income Statement [Abstract] Income Statement [Abstract] Nonrecurring fair value [Abstract] Nonrecurring fair value [Abstract] Nonrecurring fair value [Abstract]