Revenue Recognition - Schedule of Revenue Recognition (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation of Revenue [Line Items]
Total revenues									$ 6,276	$ 5,843	$ 5,971
Transaction-based expenses									1,297	1,205	1,459
Total revenues, less transaction-based expenses	$ 1,308	$ 1,200	$ 1,246	$ 1,225	$ 1,146	$ 1,146	$ 1,180	$ 1,166	4,979	4,638	4,512
Trading & Clearing Segment
Disaggregation of Revenue [Line Items]
Total revenues									3,717	3,333	3,561
Transaction-based expenses									1,297	1,205	1,459
Total revenues, less transaction-based expenses									2,420	2,128	2,102
Data & Listings Segment
Disaggregation of Revenue [Line Items]
Total revenues									2,559	2,510	2,410
Transaction-based expenses									0	0	0
Total revenues, less transaction-based expenses									2,559	2,510	2,410
Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues, less transaction-based expenses									2,074	1,813	1,791
Services transferred at a point in time | Trading & Clearing Segment
Disaggregation of Revenue [Line Items]
Total revenues, less transaction-based expenses									2,074	1,813	1,791
Services transferred at a point in time | Data & Listings Segment
Disaggregation of Revenue [Line Items]
Total revenues, less transaction-based expenses									0	0	0
Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenues, less transaction-based expenses									2,905	2,825	2,721
Services transferred over time | Trading & Clearing Segment
Disaggregation of Revenue [Line Items]
Total revenues, less transaction-based expenses									346	315	311
Services transferred over time | Data & Listings Segment
Disaggregation of Revenue [Line Items]
Total revenues, less transaction-based expenses									2,559	2,510	2,410
Transaction and clearing, net
Disaggregation of Revenue [Line Items]
Total revenues									3,483	3,131	3,384
Transaction and clearing, net | Trading & Clearing Segment
Disaggregation of Revenue [Line Items]
Total revenues									3,483	3,131	3,384
Transaction and clearing, net | Data & Listings Segment
Disaggregation of Revenue [Line Items]
Total revenues									0	0	0
Data services
Disaggregation of Revenue [Line Items]
Total revenues									2,115	2,084	1,978
Data services | Trading & Clearing Segment
Disaggregation of Revenue [Line Items]
Total revenues									0	0	0
Data services | Data & Listings Segment
Disaggregation of Revenue [Line Items]
Total revenues									2,115	2,084	1,978
Listings
Disaggregation of Revenue [Line Items]
Total revenues									444	426	432
Listings | Trading & Clearing Segment
Disaggregation of Revenue [Line Items]
Total revenues									0	0	0
Listings | Data & Listings Segment
Disaggregation of Revenue [Line Items]
Total revenues									444	426	432
Other revenues
Disaggregation of Revenue [Line Items]
Total revenues									234	202	177
Other revenues | Trading & Clearing Segment
Disaggregation of Revenue [Line Items]
Total revenues									234	202	177
Other revenues | Data & Listings Segment
Disaggregation of Revenue [Line Items]
Total revenues									$ 0	$ 0	$ 0