Business Segments (Schedule of Operating Segments) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Segment Reporting Information [Line Items]
Total revenues	$ 1,535	$ 1,651
Transaction-based expenses	(643)	(800)
Revenues less transaction-based expenses	892	851
Operating income (loss)	405	365
Operating Segments | Market Technology
Segment Reporting Information [Line Items]
Total revenues	124	100
Revenues less transaction-based expenses	124	100
Operating income (loss)	4	(2)
Operating Segments | Investment Intelligence
Segment Reporting Information [Line Items]
Total revenues	284	256
Revenues less transaction-based expenses	284	256
Operating income (loss)	184	166
Operating Segments | Corporate Platforms
Segment Reporting Information [Line Items]
Total revenues	168	146
Revenues less transaction-based expenses	168	146
Operating income (loss)	75	58
Operating Segments | Market Services
Segment Reporting Information [Line Items]
Total revenues	958	1,134
Transaction-based expenses	(643)	(800)
Revenues less transaction-based expenses	315	334
Operating income (loss)	200	226
Corporate Items
Segment Reporting Information [Line Items]
Total revenues	1	15
Revenues less transaction-based expenses	1	15
Operating income (loss)	$ (58)	$ (83)