Goodwill and Acquired Intangible Assets (Finite-Lived and Indefinite-Lived Intangible Assets) (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Finite-Lived Intangible Assets [Line Items]
Gross Amount	$ 2,248	$ 2,262
Accumulated Amortization	(728)	(695)
Net Amount	1,520	1,567
Indefinite-lived Intangible Assets [Line Items]
Indefinite-Lived Intangible Assets	1,231	1,246
Intangible assets, net	2,751	2,813
Exchange and clearing registrations
Indefinite-lived Intangible Assets [Line Items]
Indefinite-Lived Intangible Assets	1,257	1,257
Trade names
Indefinite-lived Intangible Assets [Line Items]
Indefinite-Lived Intangible Assets	121	121
Licenses
Indefinite-lived Intangible Assets [Line Items]
Indefinite-Lived Intangible Assets	52	52
Foreign currency translation adjustment
Indefinite-lived Intangible Assets [Line Items]
Indefinite-Lived Intangible Assets	(199)	(184)
Technology
Finite-Lived Intangible Assets [Line Items]
Gross Amount	294	295
Accumulated Amortization	(64)	(54)
Net Amount	230	241
Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Gross Amount	2,050	2,050
Accumulated Amortization	(740)	(711)
Net Amount	1,310	1,339
Trade names and other
Finite-Lived Intangible Assets [Line Items]
Gross Amount	60	60
Accumulated Amortization	(12)	(11)
Net Amount	48	49
Foreign currency translation adjustment
Finite-Lived Intangible Assets [Line Items]
Gross Amount	(156)	(143)
Accumulated Amortization	88	81
Net Amount	$ (68)	$ (62)