Revenue Recognition - Schedule of Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Total revenues	$ 1,634	$ 1,556	$ 3,217	$ 3,136
Transaction-based expenses	336	310	649	665
Total revenues, less transaction-based expenses	1,298	1,246	2,568	2,471
Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues, less transaction-based expenses	547	521	1,075	1,030
Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenues, less transaction-based expenses	751	725	1,493	1,441
Trading and Clearing Segment
Disaggregation of Revenue [Line Items]
Total revenues	970	919	1,896	1,870
Transaction-based expenses	336	310	649	665
Total revenues, less transaction-based expenses	634	609	1,247	1,205
Trading and Clearing Segment | Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues, less transaction-based expenses	547	521	1,075	1,030
Trading and Clearing Segment | Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenues, less transaction-based expenses	87	88	172	175
Data and Listings Segment
Disaggregation of Revenue [Line Items]
Total revenues	664	637	1,321	1,266
Transaction-based expenses	0	0	0	0
Total revenues, less transaction-based expenses	664	637	1,321	1,266
Data and Listings Segment | Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues, less transaction-based expenses	0	0	0	0
Data and Listings Segment | Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenues, less transaction-based expenses	664	637	1,321	1,266
Transaction and clearing, net
Disaggregation of Revenue [Line Items]
Total revenues	907	864	1,769	1,762
Transaction and clearing, net | Trading and Clearing Segment
Disaggregation of Revenue [Line Items]
Total revenues	907	864	1,769	1,762
Transaction and clearing, net | Trading and Clearing Segment | Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	62	65	122	128
Transaction and clearing, net | Data and Listings Segment
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Data services
Disaggregation of Revenue [Line Items]
Total revenues	553	526	1,099	1,046
Data services | Trading and Clearing Segment
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Data services | Data and Listings Segment
Disaggregation of Revenue [Line Items]
Total revenues	553	526	1,099	1,046
Listings
Disaggregation of Revenue [Line Items]
Total revenues	111	111	222	220
Listings | Trading and Clearing Segment
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Listings | Data and Listings Segment
Disaggregation of Revenue [Line Items]
Total revenues	111	111	222	220
Other revenues
Disaggregation of Revenue [Line Items]
Total revenues	63	55	127	108
Other revenues | Trading and Clearing Segment
Disaggregation of Revenue [Line Items]
Total revenues	63	55	127	108
Other revenues | Data and Listings Segment
Disaggregation of Revenue [Line Items]
Total revenues	$ 0	$ 0	$ 0	$ 0