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earnings of unconsolidated subsidiaries Income (Loss) from Equity Method Investments Thereafter Finance Lease, Liability, to be Paid, after Year Five Cover [Abstract] Cover [Abstract] Investment income Investment Income, Nonoperating Subsequent Events [Text Block] Subsequent Events [Text Block] 2028 Long-Term Debt, Maturity, Year Five Fair Value, Recurring [Member] Fair Value, Recurring [Member] Compensation and benefits Labor and Related Expense Financial instruments measured at fair value on a recurring basis Fair Value Measurement and Measurement Inputs, Recurring and Nonrecurring [Text Block] Class B Common Stock, Class B-2 [Member] Class B Common Stock, Class B2 [member] Class B Common Stock, Class B2 [Member] Cash dividends Payments of Dividends Other liabilities Other Liabilities, Noncurrent Total Operating Lease Payments Lessee, Operating Lease, Liability, to be Paid Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Finance Lease, Right-of-Use Asset, Amortization Finance Lease, Right-of-Use Asset, Amortization 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 Flows from Financing Activities Net Cash Provided by (Used in) Financing Activities [Abstract] EBS Foreign Exchange EBS Foreign Exchange [Member] EBS Foreign Exchange Marketable Securities Marketable Securities Equity Component [Domain] Equity Component [Domain] Finance Lease, Liability, Current Finance Lease, Liability, Current Class B Common Stock, Class B-1 [Member] Class B Common Stock, Class B1 [member] Class B Common Stock, Class B1 [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] CBOT CBOT [Member] CBOT Basic (in shares) Weighted Average Number of Shares Outstanding, Basic Entity Current Reporting Status Entity Current Reporting Status Lessee, Operating Lease, Renewal Term Operating Lease Renewal Term Operating Lease Renewal Term Operating Income Operating Income (Loss) Revenue Recognition [Abstract] Revenue Recognition [Abstract] Revenues Revenues [Abstract] Contingent liability to SGX, amount of irrevocable letters of credit Guarantee Collateral Guarantee Collateral Other Comprehensive Income Location [Axis] Other Comprehensive Income Location [Axis] Segments [Axis] Segments [Axis] Statement [Line Items] Statement [Line Items] Other comprehensive income (loss), net of tax: Other Comprehensive Income (Loss), Net of Tax [Abstract] Foreign Exchange [Member] Foreign Exchange [Member] Clearing Firm, Market Data And Other Customer Relationships [Member] Customer Relationships [Member] Change in performance bond and guaranty fund contributions Change in performance bond and guaranty fund contributions Change in performance bond and guaranty fund contributions Nonrecurring fair value [Abstract] Nonrecurring fair value [Abstract] Nonrecurring fair value [Abstract]