Goodwill and Acquired Intangible Assets (Finite-Lived Intangible Assets) (Details) - USD ($) $ in Millions	Jun. 30, 2026	Dec. 31, 2025
Intangible Asset, Finite-Lived [Line Items]
Gross Amount	$ 7,100	$ 7,175
Accumulated Amortization	(2,095)	(1,903)
Net Amount	5,005	5,272
Total indefinite-lived intangible assets	1,218	1,239
Total intangible assets, net	6,223	6,511
Exchange and clearing registrations
Intangible Asset, Finite-Lived [Line Items]
Total indefinite-lived intangible assets	1,257	1,257
Trade names
Intangible Asset, Finite-Lived [Line Items]
Total indefinite-lived intangible assets	121	121
Licenses
Intangible Asset, Finite-Lived [Line Items]
Total indefinite-lived intangible assets	50	52
Foreign currency translation adjustment
Intangible Asset, Finite-Lived [Line Items]
Total indefinite-lived intangible assets	(210)	(191)
Technology
Intangible Asset, Finite-Lived [Line Items]
Gross Amount	1,222	1,222
Accumulated Amortization	(630)	(531)
Net Amount	592	691
Customer relationships
Intangible Asset, Finite-Lived [Line Items]
Gross Amount	5,632	5,711
Accumulated Amortization	(1,515)	(1,432)
Net Amount	4,117	4,279
Trade names and other
Intangible Asset, Finite-Lived [Line Items]
Gross Amount	405	405
Accumulated Amortization	(63)	(53)
Net Amount	342	352
Foreign currency translation adjustment
Intangible Asset, Finite-Lived [Line Items]
Gross Amount	(159)	(163)
Accumulated Amortization	113	113
Net Amount	$ (46)	$ (50)