Performance Bonds and Guaranty Fund Contributions (Notes)	9 Months Ended
	Sep. 30, 2024
Performance Bonds and Guaranty Fund Contributions [Abstract]
Performance Bonds and Guaranty Fund Contributions	Performance Bonds and Guaranty Fund Contributions Performance Bonds and Guaranty Fund Contribution Reinvestment. CME reinvests cash performance bonds and guaranty fund contributions and distributes a portion of the interest earned back to the clearing firms. The reinvestment of cash can include certain commercial and central bank deposits, government securities, reverse repurchase agreements, and money market funds. CME has been designated as a systemically important financial market utility by the Financial Stability Oversight Council and is authorized to maintain cash accounts at the Federal Reserve Bank of Chicago. At September 30, 2024, CME maintained $87.7 billion within the cash account at the Federal Reserve Bank of Chicago. The cash deposit at the Federal Reserve Bank of Chicago is included within performance bonds and guaranty fund contributions on the consolidated balance sheets. Cash performance bonds and guaranty fund contributions are included as restricted cash and restricted cash equivalents on the consolidated statements of cash flows. In the third quarter and first nine months of 2024, earnings from cash performance bond and guaranty fund contributions were $991.3 million and $3,035.6 million, compared with $1,246.5 million and $4,042.9 million in the third quarter and first nine months of 2023, respectively. In the third quarter and first nine months of 2024, expenses related to the distribution of interest earned on collateral reinvestments were $922.6 million and $2,829.4 million, compared with $1,160.5 million and $3,756.8 million in the third quarter and first nine months of 2023, respectively. The earnings from cash performance bonds and guaranty fund contributions are included in investment income and the expense related to the distribution of interest earned is included in other non-operating income (expense) on the consolidated statements of income. Clearing House Contract Settlement. The clearing house marks-to-market open positions at least once a day (twice a day for all futures and options contracts). Based on values derived from the mark-to-market process, the clearing house requires payments from clearing firms whose positions have lost value and makes payments to clearing firms whose positions have gained value. Under the extremely unlikely scenario of simultaneous default by every clearing firm who has open positions with unrealized losses, the maximum exposure related to positions other than cleared-only interest rate swap contracts would be one half day of changes in fair value of all open positions, before considering the clearing house’s ability to access defaulting clearing firms' collateral deposits. For cleared interest rate swap contracts, the maximum exposure at the time of default related to the clearing house’s guarantee would be one full day of changes in fair value of all open positions, before considering the clearing house’s ability to access defaulting clearing firms' collateral. During the first nine months of 2024, the clearing house transferred an average of approximately $5.7 billion a day through its clearing systems for settlement from clearing firms whose positions had lost value to clearing firms whose positions had gained value. The clearing house reduces its guarantee exposure through initial and maintenance performance bond requirements and mandatory guaranty fund contributions. Management has assessed the fair value of the company’s settlement guarantee liability by taking the following factors into consideration: the design and operations of the clearing risk management process, the financial safeguard packages in place, historical evidence of default by a clearing member and the estimated probability of potential payouts by the clearing house. Based on the assessment performed, management estimates the guarantee liability to be nominal and therefore has not recorded any liability at September 30, 2024 and December 31, 2023. The company does not have a history of significant losses recognized on performance bond collateral as posted by our clearing members, and management currently does not anticipate any future credit losses on its performance bond assets. Accordingly, the company has not provided an allowance for credit losses on these performance bond deposits, nor has it recorded any liabilities to reflect an allowance for credit losses related to our off-balance sheet credit exposures and guarantees.