Revenue from Contracts with Customers (Revenue by Product, Service and Segment) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Disaggregation of Revenue [Line Items]
Revenues less transaction-based expenses	$ 1,500	$ 1,306	$ 2,908	$ 2,543
Operating segments | Capital Access Platforms | Data & Listing Services
Disaggregation of Revenue [Line Items]
Revenues less transaction-based expenses	217	198	431	391
Operating segments | Capital Access Platforms | Index
Disaggregation of Revenue [Line Items]
Revenues less transaction-based expenses	271	196	491	388
Operating segments | Capital Access Platforms | Workflow & Insights
Disaggregation of Revenue [Line Items]
Revenues less transaction-based expenses	133	126	264	249
Operating segments | Financial Technology | Financial Crime Management Technology
Disaggregation of Revenue [Line Items]
Revenues less transaction-based expenses	98	81	191	157
Operating segments | Financial Technology | Regulatory Technology
Disaggregation of Revenue [Line Items]
Revenues less transaction-based expenses	120	104	238	206
Operating segments | Financial Technology | Capital Markets Technology
Disaggregation of Revenue [Line Items]
Revenues less transaction-based expenses	321	279	628	533
Operating segments | Market Services
Disaggregation of Revenue [Line Items]
Revenues less transaction-based expenses	340	306	657	587
Reconciling items | Other revenues
Disaggregation of Revenue [Line Items]
Revenues less transaction-based expenses	$ 0	$ 16	$ 8	$ 32