Equity - Redeemable Noncontrolling Interests (Details) $ in Millions	12 Months Ended
Dec. 31, 2020 USD ($)
Noncontrolling Interest [Line Items]
Interest in joint venture minimum (as a percent)	20.00%
Change in control period	15 days
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Balance as of December 31, 2019	$ 2,268
Net income attributable to redeemable noncontrolling interest	181
Distributions to noncontrolling interest	(200)
Redemption value adjustment	532
Balance as of December 31, 2020	$ 2,781
CME Group
Noncontrolling Interest [Line Items]
Noncontrolling interest ownership by noncontrolling owners (as a percent)	27.00%

Business Acquisition, Agreement Terms, Change of Control, Put Option for Minority Interest Ownership, Effective Period

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Interest in joint venture minimum percentage.

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Change in noncontrolling interest during the period as a result of a change in the redemption value of redeemable noncontrolling interest.

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Decrease in noncontrolling interest balance from payment of dividends or other distributions by the non-wholly owned subsidiary or partially owned entity, included in the consolidation of the parent entity, to the noncontrolling interest holders.

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The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of Net Income (Loss) attributable to redeemable noncontrolling interest.

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As of the reporting date, the aggregate carrying amount of all noncontrolling interests which are redeemable by the (parent) entity (1) at a fixed or determinable price on a fixed or determinable date, (2) at the option of the holder of the noncontrolling interest, or (3) upon occurrence of an event that is not solely within the control of the (parent) entity. This item includes noncontrolling interest holder's ownership (or holders' ownership) regardless of the type of equity interest (common, preferred, other) including all potential organizational (legal) forms of the investee entity.

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