Revenue Recognition - Schedule of Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Total revenues	$ 1,663	$ 1,463	$ 4,880	$ 4,599
Transaction-based expenses	327	263	976	928
Total revenues, less transaction-based expenses	1,336	1,200	3,904	3,671
Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues, less transaction-based expenses	578	477	1,653	1,507
Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenues, less transaction-based expenses	758	723	2,251	2,164
Trading and Clearing Segment
Disaggregation of Revenue [Line Items]
Total revenues	996	821	2,892	2,691
Transaction-based expenses	327	263	976	928
Total revenues, less transaction-based expenses	669	558	1,916	1,763
Trading and Clearing Segment | Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues, less transaction-based expenses	578	477	1,653	1,507
Trading and Clearing Segment | Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenues, less transaction-based expenses	91	81	263	256
Data and Listings Segment
Disaggregation of Revenue [Line Items]
Total revenues	667	642	1,988	1,908
Transaction-based expenses	0	0	0	0
Total revenues, less transaction-based expenses	667	642	1,988	1,908
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	667	642	1,988	1,908
Transaction and clearing, net
Disaggregation of Revenue [Line Items]
Total revenues	929	760	2,698	2,522
Transaction and clearing, net | Trading and Clearing Segment
Disaggregation of Revenue [Line Items]
Total revenues	929	760	2,698	2,522
Transaction and clearing, net | Trading and Clearing Segment | Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	66	56	188	184
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	530	1,652	1,576
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	530	1,652	1,576
Listings
Disaggregation of Revenue [Line Items]
Total revenues	114	112	336	332
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	114	112	336	332
Other revenues
Disaggregation of Revenue [Line Items]
Total revenues	67	61	194	169
Other revenues | Trading and Clearing Segment
Disaggregation of Revenue [Line Items]
Total revenues	67	61	194	169
Other revenues | Data and Listings Segment
Disaggregation of Revenue [Line Items]
Total revenues	$ 0	$ 0	$ 0	$ 0