Commitments and Contingencies - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Loss Contingencies [Line Items]
Option to extend lease period (in years)	12 years		12 years
Total estimated future lease payments	$ 81		$ 81
Revenue	$ 4,146	$ 3,755	$ 8,318	$ 7,532
CME Group
Loss Contingencies [Line Items]
Noncontrolling interest ownership by noncontrolling owners (as a percent)	27.00%		27.00%
S&P DJ Indices | CME Group
Loss Contingencies [Line Items]
Noncontrolling interest ownership by noncontrolling owners (as a percent)	27.00%		27.00%
S&P DJ Indices | Related Party
Loss Contingencies [Line Items]
Revenue	$ 54	$ 51	$ 107	$ 103
Minimum
Loss Contingencies [Line Items]
Remaining lease terms	1 year		1 year
Lease term (in years)	1 year		1 year
Maximum
Loss Contingencies [Line Items]
Remaining lease terms	11 years		11 years
Lease term (in years)	11 years		11 years